I'd discuss it at length w/your vet. Even though Taz is a senior kitty, he could still come through the surgery w/no problems provided that he's in relatively good health otherwise. It surely isn't pleasant for him to have the procedure done every couple of months and it isn't easy on your wallet either. I'd opt to have it over with as long as the risks of surgery are minimal and my vet felt confident that all should go well. I'm not telling you what to do, just what I would do if in the same situation.