There's no pat formula. It depends on how much nectar is within reasonable flying distance. And you well know that that is subject to weather conditions & about a billion other things varying from season to season, year to year. As long as they have enough nectar sources & pollen sources the sky's the limit. Of course, that doesn't take into account "putting too many eggs in one basket" which is never a good idea. One wouldn't want to put them at risk of spreading disease like wildfire through the entirety of your hives if things got bad like that.
Common sense. Margaret, you have good common sense -- trust it & let it guide you.