Moisture is the big thing when washing salt from around bearings, even with the best seals. Size matters when speed rating comes into play, 60mm X110mm X22mm steel bearing are generally good to or around 6,000 Rpm when new. Who knows what that rating is, after they get a few years on them. Your right; you Probably will not turn the wheel that RPM, not even half that, so RPMs. are not the only consideration.
Safest bet for high speed over long distance is ceramic, "Hands Down". I have lost steel bearings at speed, "once", it want happen again.