Martin,
Pretty much every time I get into a new sport, I dont know what I really need and end up with too much. As I get progressively more experienced — experienced with what I don't need — I leave more and more home.
So, I'll go back to my first big canopy trek, backpacking if you will (although we wore no real backpacks) through the top of a Eucalyptus forest in Victoria, AU called Wallaby Creek. It's a closed watershed for Melbourne, but we had a permit to do some science and to do this week-long trip from tree to tree, carrying all our food, our water, and even our human waste.
This was something nobody had tried before, and likely very few had even envisioned: tree top to tree top, always over 200 feet or so off the ground, sleeping in hammocks, sliding our gear over on tyroleans rigged using magic missiles fired from cross bows and mini-grapnels snagging lanyards. It was cool! The idea is to climb one tree and then go onwards from there, with no help from the ground, no preplaced ropes, or anything.
But we took way too much stuff. We moved so slow we had to drop most of our gear and half our team to complete the trek.
I learned a lot about the top of a mountain ash forest, but I learned more when we lightened up. Before we lightened up we spent most of the time messing with gear, hauling gear, handling gear. I did learn there are some neat ant-mimic spiders, as I waited around. We told stories. But I learned less about the wilderness than I did when we travelled light and free.
Back in my teens when I had big heavy leather boots and a heavy pack filled with stuff I carried but didn't use: I looked at my feet and not at the landscape. I looked forward to the breaks more than the travel between them. I learned that my feet ached, that creek crossings were awkward and hills long and tiring.
I learned that if I carry too much stuff I sometimes forget to pack it up and leave it accidently behind, but if it was not important enough to remember, maybe it was not important enough to carry.
Most heavy trips I learn that I can hurt my back and my feet and there's stuff I carried but didn't use.
However there's one class of heavy trip I did repeatedly for a decade: family trips. One example, with my six year old son and a North Face VE 24, back in 1993. We walked 60 miles across Umnak, an Aleutian Island, just the two of us. I carried a big pack because he carried nothing. Sometimes I carried him, too, when he said "Dad, my feet hurt." but he always hopped down when I said, "Son, my back hurts."
I learned a lot on that trip! The best thing I learned was that he and I liked doing long wilderness trips together and that I liked being there with him, and liked looking after him. I found going heavy was Ok cause he needed more frequent rests too. I found stopping a lot and sharing the landscape and seascape views were good. I liked having all the stuff for him: big tent, two rain jackets for him, lots of fuel and a stove, a gun for protection against wild bulls, a camera to capture the trip, a book for us to read, plenty of snacks to keep him happy, a glass ball from a Bering Sea beach as a memento.
I have done plenty of heavy trips: with science, with climbing, with skiing, with kids, with students, with boats, with moose meat. Mostly those trips are slow and work-like, or filled with base-camp time to allow enjoyment of whatever it is we're carrying.
Not to be snarky, but the major experience gained comes down to discovering what I don't need to bring next time, followed by a self-discovery that I can carry a big pack, and finally whatever the reason I'm going heavy-weight (climbing gear, family gear, science stuff), the specific application of that burden will provide experience, and that's why I am there with it.