I bought a 1992 Hallmark almost 10 years ago thinking it would be around for a year or two at the most. We're still camping out of it. Sure, I've had to do some work along the way, but I don't think most truck camper users are going to be able to reduce a wood framed camper to a pile of sticks in any reasonable amount of time if they take decent care of it.
I would be on the lookout for a camper that was stored indoors if possible, and be sure to re-caulk the roof asap when you find one. Aside from that, find a layout you like at a price you can afford, and get out there!!
FWIW, I have a 8.5' camper, and I can't imagine having three people crammed in a 6.5' camper. I'd recommend looking at the longer campers, even if you have a 6.5' box truck. If your truck is 5.5', then a shorter camper might be a better plan, it'll just be cozy.
Hmm. I don't know where you are, but I have a friend in Reno with an older 8.5' Hallmark coming up for sale...