How to freeze unbaked pies?

When I go home for Christmas I want to make several pies and then freeze them so my dad can thaw and bake one every now and then when I'm not there. I'd like to do sweet potato/pumpkin and a few fruit pies. I'll probably use pre-made crusts and my own filling recipes. Can you freeze unbaked pies or do bake them and then freeze? Either way, what's the best way to thaw and prepare them later? How long can they stay frozen? Thanks!