Hypothetically, age probably isn't a factor, in and of itself. I think it's more a case of knowing when to go and actually making yourself go before it becomes a problem, and most people over, say, the age of five usually understand the timing thing. But I suspect that if, for some reason, you were prevented from going when you knew you really should, you'd be doing "the potty dance" all over again!
Are you planning a vacation get-away for this summer?