I use two of these during the winter months on the cabin sole. They were given to me two yrs ago from two different sources. Several days ago, I took them to the boat and plugged em in..I always check the fan to see if it’s turning. Being that they were used when acquired, I did (do) not know what a new one “looks” like WRT to fan speed. This time, one of them had a very slow noticeable fan speed. Took it home and disassembled it and put several drops of “McLube One Drop“ on both end bearings of the motor. Reassembled and WOW! What a difference. Going to do it to the other one. Being these are aboard and running unattended 24/7, I think this might be a yearly maintenance item..They are thermally protected, however....