I've used the compressed paper seals as well as the nylon ones. In my experience, I've had to crank down harder on the paper seals to get a good seal. And I generally use the nylon ones for two fills, though I occasionally do some regulator work and remove the regulator. So 3 or 4 times per seal I'll remove and replace the regulator.
I don't think I'd try to reuse a paper washer, though I can't recall if I've ever put one to the test.
Those nylon seals are dirt cheap via Evilbay, by the way. Just do a "co2 washer" search.