I want to do it, and yet, four weeks, oof, that's a lot of time that another plant could be in that spot flowering up a new pile of buds.
You don't have to give up a whole female though. You save the pollen in a little vial. Then you put into flowering some new clones, from the same mother (e.g. same genetics) as the female that gave you the pollen after over-flowering. Then you wait until 2-3 weeks into flowering or whatever, get a fine brush, and paint a couple of stalks with the pollen from the vial. You get two seeded stalks (or whatever you want), but the rest of the plant is normal.
That is (supposedly) how to make feminized seeds, or at least a way. That's the method described in Soma's book, which I have somewhere, but can't find because I'm a stoner and misplaced it. Heh. They have to be the same genetics though, e.g. all plants involved are clones from the same mother -- the pollen-producer and the ones you paint with the pollen a generation later.