On the top of my case I've been using two Cooler Master fans that came with my case. They've worked fine, and it has been a few years since I purchased them. The problem I'm getting with them is that during large changes in temperature (such as having a hot room in the winter, and opening the window to let the heat out) the fans start to scrape and click, which I assume is due to the expansion / contraction of the fans themselves (note that these fans work perfectly, and quietly, otherwise). I want to purchase new fans, but I'm unsure what to look for when it comes to fans that simply won't have this problem. Is this something that comes with age? Or is there a style / material that would otherwise not be affected?
So, if I were to buy new fans based on cooling / decibel level / price, would I be safe in assuming they would not have the same problems as my old fans (which would only possibly develop a number of years down the road) or do I need to specifically find fans built to undergo changes in temperature (in which case, what do I look for?)?