Stockish or 1-3" lift, definitely keep them... as you lift the truck beyond that, they are potentially less necessary on the street, as you'll hardly be able to touch them. Off-road, they are even more important, in that they prevent inversion, but as you lift even beyond 6", it becomes harder to touch them -- but when you do, muy importente!

If you have good enough springs to flex to extremes, bump stops are critical... most folks simply don't get enough flex to benefit from bump stops on high-lift trucks, unless they resposition the bumpstops lower...

Note that your bumpstops may also protect your exhaust and shocks from getting smashed/broken.

Randii