I should have explained why I said that. If your storage is on an SD card constantly updating a log file can shorten the life of the card, though I guess just the one file a few times a day won't have much impact. Mine is stored on a RAID array on a server so it isn't an issue for me.
No, no resistance. I connected the fan to +5v and the collector, emitter to GND, GPIO pin to base. (I think that's right, got it the wrong way round when I first typed it.)