Well, simple math would suggest that, if Mr. Car Stereo Company off roads his truck a fair amount, combined with lots of high mileage, that his shocks would need rebuilt roughly every 25k miles, maybe even sooner depending on how intense of off-roading he's doing. Say his truck has 250,000 miles on it, with shocks getting rebuilt every 25k miles.....that would be 10 total rebuilds. So this hypothetical scenario would then indicate, that he very well could be on his 7th rebuild, and have never replaced the motor or trans.
And yes, if your truck is a daily, or your only vehicle, definitely would be beneficial to keep them, or if you simply don't care, there is a market for them for sure!