My previous truck, a 2000, had a spray in bedliner that was still nearly pristine after almost 16 years. Only place the truck wasn't rusting, too. 
Seriously, the guys at the local body shop told me that a lot of guys have their rocker panels sprayed with the textured liner when the rocker panels start to show too much rust. Pretty much stops the rusting for a while. Now I know to look for that when looking at older trucks.
Seriously, the guys at the local body shop told me that a lot of guys have their rocker panels sprayed with the textured liner when the rocker panels start to show too much rust. Pretty much stops the rusting for a while. Now I know to look for that when looking at older trucks.