Just room temp. A "cool dry place" is always preferred, so our boxes are on the floor and under a table. Humidity for the seeds is low since most are sealed up.

There's no need to refridgerate or freeze them. Although some seeds perform better if they've been "cold stratified", but that's probably best to do just before planting.

Seeds have been found in the backs of caves and germinated after hundreds of years. I'm willing to bet the germination rate was lower, but if they're kept away from extremes, or conditions that will cause them to sprout, they should be fine.