Can you keep cigars in a wine cellar?

A: Absolutely. A lot of cigar smoking wine enthusiasts have made room for their cigars in their wine cellars. You can even buy a combination wine-rack & humidor (see photo).

Moreover, in a way, you also answered your own question. For long term aging, cooler temperatures are quite acceptable. As long as you keep the RH in the humidor at a proper level, your cigars will be fine.