Unfortunately, you are going to have to sit through my app development thoughts before you get to the traditional backpacking lessons learned. Hope you find these useful!
Hikers Assistant iPhone and Apple Watch Apps
Hikers Assistant for iPhones and iPads has been on the Apple Store for a year and a half now. I developed it after my first AT attempt, and I've been improving it ever since. However, I had never used it in high mountains where elevation seemed to be my first priority, and I found some shortcomings.
For the last couple of months, since I got my Apple Watch Series 2 with GPS, waterproofing, and a better battery, I've been working on a counterpart watch app. Basically, the watch app gives you everything but big maps, and lets you do most critical functions without pulling out your iPhone.
Well, the watch app worked nearly perfectly. In fact, the only problem I had was when I wanted to start the trail, and I couldn't get a GPS reading (iPhone or watch) in camp. We were surrounded by mountains and under tall tree cover. I suspected a larger GPS error, but I didn't expect to not be able to get a reading at all. I can try accepting more error and allowing more time for a fix; and I will need to have some backup in code to handle such a situation. It won't be easy for me to replicate those conditions.
As to the iOS app for iPhones. We wanted to know what the elevation was at Columbine Pass that we were headed to. It was on a route in the app, but I didn't have a waypoint set at that location, and hence could not get the elevation. The day I got back, I added the capability to touch the trail and get any location's position and elevation.
Also, somehow with the GPS problems, I added a route to the set that had no route points on it. That caused my Route Editor screen to close the app whenever I tried opening it. And that meant, I couldn't see the elevation profiles of individual routes--such as the one going to Columbine Pass. I've fixed that too.
The last thing that bothered me was an inability to modify routes in the field. I had expected to do full tracks logging each day's hiking. But with the GPS problems in camp, I couldn't start the tracks accurately. Plus, everyone wanted to hike at top speed, so I didn't want to do quick stops to try and correct the issue with my iPhone. I had complete routes set up, but we were only doing partial ones due to our reduced elevation stamina. Since GPS was spotty, that left the pedometer on the iPhone and watch, but neither is very accurate. I want to be able to split routes in the field to help me get accurate estimates of miles and elevation changes.
That's enough on the apps...
My whole fishing rig, including tackle is only about 7 oz. But the Tenkara pole is easy to damage and is still 24" when collapsed. I have to protect it in my pack. It was hard to attach to my day pack. And we didn't really get to any good fishing spots! This is the third time I've taken a pole on backpacking trips. Only one of those resulted in actual fishing where I caught anything. Bottom line, unless a short, easy day is planned by water, or I camp next to a lake or nice stream, don't bother carrying the fishing gear. When I'm solo, I seldom plan short, easy days.
Acclimating to High Altitudes and Peak Bagging
I knew from my Montana trip that I wouldn't have the same lung capacity as at lower altitudes. I'm pretty confident now that I won't get altitude sickness. But I had serious issues with getting out of breath on the uphills above 11,000'. It was a lot better by the end of the trip. My take-away is that I really need to allow time to acclimate to high altitudes, especially if I want to climb any 13,000 or 14,000 peaks. I had thought about doing a week or two before this trip on the CDT or CT. In retrospect, I should have done that. It would have gotten my legs back in shape for climbing and allowed me to acclimate to the altitude. However, I didn't have a problem with the leg muscles, we just never went far enough!
Carrying a Day Pack
My backpack was a 19 oz Zpacks cuben Arc Blast. My daypack was an old 23 oz MountainSmith Touring fanny pack made of heavy nylon. I like the fanny pack for day hikes at home. But stuffed with rain gear, food, electronics and 4.4 pounds of water, it did not ride as well in the mountains. Plus, it got wet and dried slowly after the afternoon storms. I switched and used my Arc Blast on the last day hike, and it worked much better, especially at weight distribution. I need to consider alternatives, but I won't take along the MountainSmith again.
Electronics and Power
Since I expected to have to charge my Apple watch daily, I took along a BigBlue 10,000 mAhr external battery. It has a short lightning cable, a short micro-USB cable, a standard USB port, and enough power to do four full charges of an iPhone 5S. I also carried a one foot charging cable for the watch and a one foot lightning extender cable. The BigBlue is only 7.73 oz. I was pretty happy with the weight and the performance. The watch didn't take but an hour to charge, and I charged my iPhone three times. But neither device got much below half a charge, even with full usage of GPS on the trail.
Food is always an issue with me. This time, I lost no weight, but I reduced my body fat by 0.3%. That means I added a bit of muscle, probably in my legs. I took 1.5 serving portions of Mountain House freeze-dried dinners instead of my usual 1.0 serving portions. And I supplement my dinners with a protein 'shake' and freeze-dried fruit. I will go back to 1.0 serving portions. I just felt stuffed.
I carried the same snacks I would take on full-day backpacking. It was too much. And the others never seemed to stop for breaks (at least Steve snacked on the go), so when I did, it meant I fell behind the others. I still believe my plan of snacking on a quick 3-5 minute break every hour is the best thing to do. It gives the leg muscles a short break, and it keeps a small drip of calories into my system. But with this group, I would cut back on my snacks.
My lunch was again peanut butter and jelly on a tortilla. I really like the combination, and will plan to keep something similar along for future lunches.
I did the altitude/temperature difference calculations based on weather predictions for Durango, and expected lows of about 32 deg F (it never got below 37 degs). Plus, my friends were predicting lots of rain and afternoon storms. With variability in weather, I took a 20 deg down quilt instead of my usual 30 deg quilt. And I had a fleece sweater in addition to my down jacket. Both were overkill. I never used the down jacket. In the quilt, I only kept the base layers on. And my head sweated in the fleece cap! I should have stuck to my ultralight principles. Add extra clothes when it gets cold at night. And don't bring unneeded insulation.
First Aid Kit
This is an unusual topic for me. I seldom have more than bug bites or scratches. This time, I got the small puncture wound from a stick while digging a cathole. I didn't have multiple bandaids or small tweezers. I really need to add a couple of ounces and beef up the kit.
This was a rare trip for me. I usually hike at low altitudes and don't try peak bagging. But the scenery here was better, and there were new challenges. Even though I wasn't sure I would make it to Windom, I do regret not trying. I want to go back! If I try to bag a peak in the future, I will do my best to get acclimated. I will also start no later than dawn to avoid storms.
Doing a group trip has both its advantages and disadvantages. Going solo, I go my own speed (highway or trail), and never feel pressure other than meeting my own expectations. On the other hand, it was really nice having folks to talk to at breakfast, lunch, and dinner. Plus, it provided extra safety on the trail. I really enjoyed the company, and hope I contributed in some small way to their enjoying the trip too!