i bought mine at Dick's sporting goods called the "carbon giant" its got reinforced sides(feels like it might be that stiff plastic cardboard type stuff) and filled with mostly cotton from what i can tell...
it stood up for 2 full seasons now...i cant imagine how many arrows from me alone..plus ive had buddies shoot it many times...
when i buy a new one, it will be one i KNOW i can get a replacement cover for. thats the only part that wears out. mine wore out so i started shooting the back...filling came out the hole in the front and i started to bury arrows real deep...never had a pass through, but had to pull many from the back.
my temperary fix?? silt fence. made out of a similar weaved material...i wrapped it in it and used a staple gun to staple into the sides...put a couple layers on...worked pretty well...needs redone...good thing i brought home a ton of silt fence...asked the boss what we did with the stuff i was ripping down and he said throw it out back at the shop...asked if i could take it...he said sure....
heres a pic
takes alot of shooting to wear out a bag with a decint cover on it...lots of room to shoot at, and the way the bag is weaved lets alot of arrows in without making a hole...
for fieldpoints, i dont usually shoot anything but my bag...arrow removal is stupidly easy....