Stud hi - how quickly do you give someone credit for roll-ups?

[Micturition Man]

About 3 times that I can remember I have seen the following sequence:

Baby card limps, I complete the bet with some big card up, a smaller card calls my completion, and then the original limper reraises.

All three times this has happened the original limper had roll-ups.

It feels hugely exploitable to just fold your big pairs versus a small card limp-reraise, but might this be a good idea in practice?

If you can fold outright on 3rd versus roll-ups it's a huge huge savings... and yet I never do because I'm always expecting my opponents not to be so freaking obvious and to actually have something like 987s or at least buried AA/KK.