Freezing butter tarts
I always run down the logic in these situations....
I see frozen butter tart squares in the stores all the time. I've also seen frozen butter tarts there. So, they must be freezable.
I agree with Kelli....I'd want to crisp them a little.
The other option would be to freeze the shells, as they are the long part of the preparation, and make them up with the filling, the day before.