I'd think it would be better to introduce them after brumation. The only reason I say this is because I've had experience with numerous reptile species that will not copulate with their cagemate at all, and when the cagemate was removed for a month or so, then returned, they go ahead and get it on. I think they get too used to the partner when they are together all the time, but when they are suddenly introduced under the right conditions, they go at it pretty fast thereafter. Just a little info from personal experience. I've experience this with geckos, as well as with ball pythons. Hope this helps a little. It makes sense to me though when you think about it.