Sometimes I will soften my ice cream in the fridge for 20 minutes or so before serving it, it tastes better when it's a little less cold. I wouldn't leave it much longer than that if you have any intention of refreezing it though. If you just want liquid ice cream I would say a week.

In the freezer I would say a month or so. Ice crystals form in and on the ice cream and leave it with a strange texture and flavor. Probably not an item you should stock up on for the year, no matter how good the price.