I've read you can store seeds in the freezer for years and they're still fine after. For killing any moths that may be in bird seed, the bag should be frozen for at least 48 hours. You can keep the seed in the 'fridge after making sure any moths or larvae have been killed in the freezing process. We've never had a problem with our bird food being at room temperature once we've taken it out of the freezer though.
I've kept Buzzy's extra seed in the freezer for several months, and it's been okay. I don't go past the expiration date on the bag, though (if there is one), but that's just because I'm extra paranoid about what he eats. His base food is Harrison's mash, and I keep that in the fridge once the bag is opened. They say it's okay at room temperature for six weeks, but again, I'm a bit paranoid when it comes to my birdie!