Seeds will last for "several" years at typical room temperature, in the dark, with normal household humidity. I prefer paper envelopes for storage, because you can store hundreds of seeds each - from many strains - and it doesn't take up much space. Plus, you can make notes right on the envelopes, as you see fit.
I have found that seeds last longer (yield better results) when kept at a fairly constant temperature, indoors; than they do when exposed to wide temperature fluctuations, like out in the garage.