My oldest is very sociable. We find that once or twice a week is plenty of time for him to form friendships at cubs, our homeschool play group that meets twice a week, at taekwondo, at swimming - all his activities actually.
AS their needs change you can change the environment to suit their needs. Even with being a social kid I find that sometimes Aiden needs a few days here and there where we don't mix with others at all.
His best friendships are still formed when he is around other kids who get how he thinks - ie other gifted kids. And those interactions really don't need to be more frequent - they just need to be happening enough for the kids to have free time to chat, play etc together.
