...we've had our camper permanently on the Silverado 2500HD, extended cab since 2006.4
We took it off for the 1st time in 7 years last fall (11/14), because we stored the camper out-doors for the 1st time in its 9 years, and, I had major camper repairs to do this summer on the camper tub.
NEVER had a problem with a garage service center servicing the truck with the relatively large pop-up on-board.
I checked the spring distance when the truck was new, before we had ever bought a camper, the our truck's springs are just about the same height with camper off in 2014, as they were back in 2004.5 when the truck was brand new out of the showroom.
We are keeping the 2004 Silverado 2500HD (see signature) indefinitely; it is in near show-room condition still today (being stored its whole life in a heated winter storage facility since new). The only thing I would suggest to anyone with a near-mint truck over 7 years old: have it professionally re-evaluated for insurance purposes, because as mint and perfect as your "baby" may be after say, 10 years, you will only get 10 cents on the dollar if it is totalled in an accident, and you will have to spring about $55 ~ $60 grand for a replacement full-sized truck ($76 grand up here in Quebec for a direct replacement!!).
A daily driver (used) can be had just about anywhere in North America VERY cheap.