If you want to freeze the seeds, you need to make sure they are completely dry first and properly sealed.
I would rather go for a fridge personally, the temps are low enough to store them safely for a few years.
Using them after being cold, it's important to let the seeds get to room temperature before opening the pack.
Cold seeds will get condensation on and if you're not planning on using them all, what you put back in the fridge or freezer has a high chance of being damp and that will cause trouble.