If you're not using a heat source you can just let them sit for at least a month. A few years back I had a marginal amount (about an ounce of dried Mt. Hood, I think), in a little drying tray I made. They were rigged up to sit such that the exhaust from my dehumidifier was blowing on them and I forgot about them. About a month later, I wanted to dry hop a beer and headed over to the part of the cellar where my hop freezer and the dehumidifier were located. For some reason I happened to look over at them and decided to grab a handful and see what they were like. After a quick rub~n~sniff, in the keg they went. First time I ever dry hopped with Mt. Hood and will do it again (if they ever produce - not a happy variety at the B-Hoppy compound). The aroma was wonderful. I will say though that that part of the cellar is pretty dark and the temp usually never goes above 70 degrees. All in all, I'd say you're good to go!