"In the list of questions in my initial post, I asked whether it makes a difference if one is carrying the light weights we do and if heavier packs make it necessary to use orthotics. As I indicated, it did make a difference when I carried 45+lbs on my back. Or at least that is what I thought."
In my case, there really does seem to be a difference. When I was a Marine road-marching with loads between 45 and 90 pounds, my feet routinely hurt. It was a "duh" sort of acceptance of the obvious (pounding boots on pavement with heavy load = pain). But when I through-hiked the AT in 1999, I was surprised that my feet hurt so badly. I was wearing quality boots and my pack was never over 50-something pounds, with my average load being about 40. A cakewalk compared to the Marine Corps and my pace was quite mellow. Yet my feet were always sore.
Move ahead a couple of years when I begin to work as a bootfitter for REI. I tried superfeet and found them very uncomfortable at first. I have a wide-heeled, relatively flat foot, which is exactly the opposite of the shape of superfeet out of the box. It took about a month for the shape to conform enough that my feet were not somewhat sore after wearing my orthotics for more than a few hours. But after that month, they began to feel great.
At this same time, I began working as a NOLS instructor (heavy loads - pack of about 22 pound, then add group gear, climbing gear, and 10-12 days of bulk food at a time = about 65 pounds at the trailhead). Even with these heavy loads, and both on and off-trail travel, I never experienced the foot pain of my AT through-hike.
Since I have gone with progressively lighter footwear and lighter packs on personal trips. I have walked shorter weekend trips and noticed soreness in the arch of my foot with factory insoles. With other after market insoles such the the Viesturs line from Sole, I actually experienced ankle pain, perhaps because they did not provide the suppination control I get from superfeet. But with superfeet, I very rarely feel such foot pain. Break-in time is uncomfortable, but otherwise I am much happier with them. Even dayhiking with a tiny pack, I notice a difference. Some may suggest I have weakened my feet by using orthotics, but I would contend that my feet hurt without them before using them, so I don't feel that I've lost much by using my superfeet.
I DO feel that orthotics such as superfeet may be overused however. Most of the customers who buy superfeet buy them for arch support. The primary purpose of such orthotics is supposed to be in reducing pronation and suppination, with arch support a happy side benefit. I believe the biggest issue in such problems is poor fit. Boots which are cut so they provide excellent arch support and heel alignment might prevent any need for many people to use orthotics.
However, I firmly believe the majority of hikers on trails have poorly fitted footwear. I see many many customers arrive wearing shoes which are not only too short or too long for their feet, but which offer a last that bears no resemblence to their foot shape. A well-trained and experienced bootfitter can make a tremendous difference, but I can honestly say that at my REI, we have decently trained but largely inexperienced footwear staff. And my store is likely one of the better stores for this department. The average small outfitter likely has no one with real footwear training, particularly if one or two people are the entire store's staff on any given evening.
Proper fitting could dramatically reduce the need for hikers to use specialized footbeds, particularly now that many brands are putting quality footbeds in their factory models, rather than the paper thin inserts of past years.