Boys jeans

Where do you buy boys pants that don't get holes in the knees? My older son is very hard on them. I don't have a single pair of jeans to pass down from him that aren't destroyed! This year I decided to buy his jeans from Shopko because they guarantee they will last until they grow out of them. If he gets holes in the knees before he out grows his jeans, I can trade them in for a new pair. I plan on doing this fairly soon. I know someone else that does the same thing at Sears for their kid tough guarantee as well. They are really good about exchanging them. It is best if you get a style that they normally carry, because they like to do an exact exchange, but they have let me do a like trade, when I went to exchange a pair that they no longer carried. (It was just a bigger pain).