I would not suggest it personally. But never say never. If they have been alone why mess with it?

Any place you can find females, you will be able to find males. So if the oppurtunity arises to get females, just get an established (or young) grouping with both sexes.

If you ever do decide to introduce them to others, then I would follow the same protocols used when introducing gerbils and other territorial rodents.

Bruce