If I finish March to october with a team can I turn around and do it again with the same team for more affinity points?
Yes if you have the patience of a saint
Yes, but right now the cap for team affinity is 70, so you can't try and get ahead for when the new content comes out.
Oh well there goes that idea then
What you can do is start seasons and get them a game from the rewards. It's not the whole thing, but it's a nice little headstart. Plus, the first half of the season is what takes the longest too.