Sure, close them up, I toss the individual bags in a small ziplock freezer bag, get as much air out as you can, and toss them in the freezer. My HBS sells pellets in 2oz packs, which means I often have enough left over for a second batch. Ideal is one of those vacuum sealers.
I just put them in a ziplock, squeeze out the air, and throw them in the freezer. I try to use them within a month or two, after 3 I toss them (only happened once).