To prevent a dried blob of sealant sitting at the bottom of a tire, either keep rotating it occasionally or drain it. I've had a rear tire on a trainer go flat because the sealant dried up. I had to add more sealant. I actually try to ride outdoors whenever possible in the Colorado winter. We get snow, but my local roads are well maintained and the snow usually melts off quickly. I don't ride below 40 degrees either.