...our camper (varies from ~1140 LBS to 1390 LBS depending on what is stored in it) has been on our truck (2500HD Silverado gasser ext.cab, 2004.5) since May of 2005; that's 8 years this past May (minus a 4 month storage stint over this entire time) !
I measured the distance from top of axle to bottom of bed on both sides when the truck was new, before loading camper (for various reasons), and after deciding to remove the camper at home, foregoing paid storage for the 1st time this October, the axle-to-bed distance is virtually the same on the unloaded Chevy (only varies by about 1/8th of an inch left to right).
The rear springs are as rock-solid unloaded today as they were when the truck came out of the showroom in 2004.
I suppose if your camper were perhaps 2000~4000 LBS sitting on your truck for 8 years, there could(?) be a noticeable change in your rear suspension...
*we have no suspension aids on the truck whatsoever since new; we don't and haven't run the jacks down to relieve weight over the past 8 years (with the exception of the 4 month stint as noted above). Your mileage may vary