I too tend to keep my cars for a long time (8 to 10 years), though I don't put on as many miles. I bought a Sport almost two months ago, with the sand colored cloth seats. Right after my purchase, I regretted not getting a Touring (I didn't even look at one) as I thought I made a mistake in foregoing the leather seats.
Now I feel better about having the cloth. I have had them treated to guard against stains so I am pretty confident that they will continue to look good. I have also found that the cloth tranfers less temperature than the leather. For me, the fear is getting in and having cold seats, for you, (I think I saw you are in Florida), you'll have the opposite problem -too warm.
I haven't had any cause for concern about the quality of the cloth seats themselves in the Sport model. (I am not thrilled with the carpet, which I believe someone else cleverly described as cardboard covered in felt. But I believe that problem runs across all trims.) My last car was a 97 Mazda Protege and after ten years, the light colored cloth seats looked just fine and had no damage. I have no reason to think these cloth seats will fare any worse. Indeed, the CX-7 cloth seems much much nicer.
Your answer may depend upon how you'll use the CX-7. If you have a big dog that would have the run of the seats, I would get leather. But if it is for you and other reasonably well behaved humans, I think you'd be fine with cloth.
Good luck making the decision. I don't think you can make a bad one. It is such a fun car to own.