thanks for the observation, asv, and the question. i'd be inclined to agree with your friends; although some seasonal fluctuation is fine, 80 degreees is pretty hot and 40 degrees is pretty cold.
makes me think of the christmas cartoon (i think it's "the year without a santa claus") with mother nature's two sons, the heat miser who could never have it too hot and the cold miser who could never have it too hot. (hmmm... i'm thinking about christmas so it must be july.)
anyway, sorry for the digression (mea culpa, but it is a holiday weekend). to conclude, i would certainly suggest a temperature-coltrolled wine cellar for you, and the brunello.