Do not mistake the purpose of springs with that of shocks.
Shocks dampen. Period.
Take a ride on the freeway, when you hit a good bump, or transition in the road that is big enough to uncompress the suspension a bit, does your truck act like a pogo-stick?
If so, you need new shocks.
Im still on the original shocks on my '94 f-150. They are all still functional, but not nearly like they were when new. They will be replaced soon.