Absolutely. When you replace 4 bad shocks with new ones you should notice a big difference in the ride quality. If you don't feel an immediate improvement then you have some serious suspension, frame, steering and/or alignment issues to dig into.
Based on the suspension design used on these trucks (1/2 to 1 ton) I would expect that generic quality shocks would only last 10 to 15 thousand miles. After that many cycles they will most likely be less than effective.That is assuming you actually use it as a truck. They are in my opinion a major wear item and should be treated as such.
Jeff