Shoes? You have drum brakes on a 2006 pickup truck?
I don't know what the heck GM was thinking there besides lower cost but if the shoes are still good after 90k miles then they are most likely not adjusting properly and barely working.
well, if he's done 70k on the front and 90k total and hasn't run over too many people, then they must be working ok. i agree that they should be pads, and not shoes. i'm going to guess that it's an hd? i haven't had anything smaller than a 3/4 ton since the late 90's, but i haven't heard of anything small (6 lug wheels) going that long on brakes. if it is an hd, i think you're in the range for normal operation.
it also kind of depends on how you put your miles on. i have an 06 2500hd and i've got mid 50's on it now, and all my brakes are showing plenty of life left. i'm going to guess 80k range when i need them, unless the rotors start to pulsate too much before that. i do a lot of short trips on local roads. if you do a lot of start and stop, you probably won't get as much life as if you do more long trips too.
the hd's aren't all that much different from the smaller trucks, but with the heavier brakes you'd assume they should last longer. also, if you haul a 2 axle trailer, your trailer brakes are taking a lot of the load off.
edit: now that i think of it, a friend bought an 06 1/2 ton wt, and i almost think it did have rear drums still. historically, all the older trucks i have had went forever on the rear shoes, as compared to the front pads & rotors, so probably not too far off. my 01 3500 and 06 2500 both have rear disc, so i tend to forget about drums. least i think they still had them on some models then?