All of them? I put them together once every other week for a few days, until I see an ovulation or the season "ends" and I stop seeing locks. I'll slow it down to once a month if I'm seeing a lot of blood around the boy's vent (my black pastel George is so enthusiastic, he's leaving streaks on his pied girlfriend's white patches. YUCK.) I'll also slow it down or even just stop pairing if the boy has been hunger fasting for several months.
Is that what you're asking about, the boys who stop eating and lose weight like crazy? That would probably depends on the boy: George the black pastel is 1300 grams, so he has a lot of weight to spare. My piebald boy Winston is only 600 grams. And Winston's got two girlfriends, so I'll have to keep an eye on his eating habits and weight.