Having had mastitis in two of my dry cows this year, I would keep them on short pickings until the udder is well and truly collapsed. Might take a month or longer, although with calves of those ages, hopefully not longer.
And yes, normally one doesn't let them back together until after the cow has her next calf on her. If you need them together, then I'd agree with Buttermilk, keep them apart for two months.