I have had my table in the loft of our shop/barn for about 4 years now, I think. There is no a/c in the summer, but we do have a small fan up in the loft, and a large fan in the shop space downstairs. It is a true loft type set-up, with only a 1/2 wall up front. A small section of this wall near the stairs, is molly-bolted to the floor. This made for a very easy delivery and set-up for the table, as the wall sectioned was removed and the table parts/slate were just slid onto the 2nd floor from a truck bed. Also....we actually added a slight 'crown' to the floor, to accomodate the extra weight of the table. With the table installed, the floor became more level with the weight of the table, instead of sagging the floor slightly. Works out great that way. Our 2nd floor can handle a lot of weight.
In the summer, we open the windows and let the place cool to a managable temp...ususally early evening...before we go up and play. The table plays great in the summer!
In the winter, we have a large wood stove installed downstairs, just forward of the 2nd floor loft. This allows for the heat to rise up to the loft. However, the loft needs to be heated for a good hour before the table is warm enough to play well on. It can take a while for the slate to come to room temp, and the cloth will play painfully slow, as a result, if you do not give it time to warm. If you have a cover for the table, be sure to remove it as soon as possible, to allow the cloth to 'breathe', that will allow any trapped moisture to escape while the table is coming to temp.
Keep the cloth clean....I brush before and after. And inspect it often. If you are having any kind of problems due to temp changes, it will usually show itself in the cloth first. Also, if you have drop-pockets, inspect the nails used to attach the pockets. Because of the temps changes, causing the wood to expand and contract, it can actually cause the nails to start backing out....and that's gonna chip some balls if you not careful!!
Lisa
Other than that, I have noticed no other problems...and we use the loft quite often, at least 2-3x a week.