The Regression Ray isn't limitless in number of uses, although I did see Patz say he wished he had made it that way, when it was retired.
Unlimited uses aren't too bad for an age-changer, but an unlimited species-changer probably wouldn't be very good at all. o3o If this does happen, then definitely not very many uses. Otherwise people would use 'em repeatedly until they get what they want - almost like a very expensive but inexpendable morphing potion.