I buy my T7 at Wally worlds close out prices and take all they have left. Last year it was 5 bottles. I store it in my basment, a room I store all my reloading powder and primers in. I do not have a dehumidifier in there or any part of the basement for that matter.
The lids are kept on tight untill I am going to go shoot then I replace the lid with one of those with the pour spout and cap.
I have never had a problem with any powder clumping Nor have I had a problem with primers. It does get damp in the summer as the water pipes will sweat.

Al