I personally don't think there is anything wrong with them coming into their first heat cycle. It is very manageable. Some pups keep themselves so clean that you rarely notice they are in heat. It does attract unwanted attention, from the opposite; but if you keep them at home than that should not be a problem. First heat is longer than others but it isn't to bad.
When I worked as a vet tech, our vet always recommended to wait until they are mature, usually after the first year. That way you are not messing with any personality or body changes they might experience. After all who wants to go through menopause that early
