g.m.
Funny you mention alpinism. Alpinism was maybe the original UL. Obviously "heavy" UL, but none the less, for a long time alpine climbers have worn all of their clothes without removing any, for an entire trip, with a sleeping bag for bivouacing in, a water bottle and some snack food. The rest of the 45 pounds was ice axes, ice screws pitons etc, what I refer to as "mission hardware".

Now days I just put what I need into my pack and carry it regardless of what it weighs. The summer I went 450 miles I never let the base weight go over 18 pounds.

I think the philosophy of not carrying the items you never use, regardless of what they are, has been the final concept which has brought my base weight down. That and the concept that I was at one time willing to spend $10 per ounce to lighten the gear.
Jim