I run the circ fan all the time as well, but the bearings on the motor do have a limited lifetime. Ask me how I know this.

A new motor will cost hundreds of dollars, more so if the blower and fan cage are a single assembly. You'll need to amortize that cost into your comfort level.

It will also quit at the least convenient time, following a combination of Tuttle's and Murphy's Laws. Again, ask me how I know this.