>>2792834>45 lbs>1000dA stock Alice will carry 100lbs easily, despite being made of thin polyester that's probably 250d or thereabout. Modern high-level military packs, made to carry 150lbs during jumps and also provide abrasion resistance, are made from 500d most of the time.
The only packs using 1000d are those made for civilian larpers, who just want "the best" without bothering to consider whether they actually need it.
The part that actually fails most of the time are the stitches, not the fabric.
tl;dr: 1000d is overkill. Just make sure the stitches are properly made (stitched 2-3 times, corners sewed back at least 1/2") and any pack will work.
Also, if you're actually going to "carry" (and not just throw in a truck) 45 lbs, you'll want a proper frame, so if you want to buy new, you'll be limited to Alice, Savotta L or XL. Any of those wll outlast you.
