I have the stamina 40 which as far as I can tell is the same as the endurance but without the webbing. To be honest I was not happy with it at all, the back was not stiff at all so pretty uncomfortable on my slim (but not soft!) frame with weight in it, the material used for all the straps is very shiny and smooth so they do not stay tight at all but loosen quite quickly including the shoulder adjusters which was very annoying, the gluey waterproofing on the material around the snow baffle (?) pull cord started to peel off after just 1 or 2 uses. without support or straps that stay tight it was just like having a loose sack swinging around on my shoulders and tiring me out!
Ok as a cheapish bag to get mucky and chuck mucky stuff in but I certainly wouldn't want to use it to put much weight in and carry for a long time. I went winter bothying with it a couple of times, just one night, and it really wasn't up to bearing the weight.
Sorry to be a misery guts but I always like to see negative feedback if I feel it's honest!