I bought a $100 mountain bike from Academy (seems to be the same basic price ranges as Wallyworld). I had it about a year. I took it offroad twice, riding slowly on fairly smooth terrain, not jumping or anything, and both times, I had to replace the rear wheel. I was forever adjusting the derailleurs, and most of the time I had it, it either would not go into high gear or into low gear, and would pop out of one gear into another or make the awfullest racking sounds when you put the power to it. The brakes were okay when new, and went downhill from there, until it was getting scary there at the last. So the bikes may "last", but that doesn't mean they're in good riding shape, either. That bike was finally stolen, and I pity the idiot that stole it. It wasn't worth hauling over the fence.

By the way, if I remember right, that bike was an "Ozone 500". But I have seen other "Ozone 500" bikes that look nothing like it, so don't pay much attention to the names.