If you open the case to service it...

If you open the case at anytime to service it or have it serviced than blow it out with a can of air at that time. Make sure your cables are not in the way when you close the case. Some tech places use air compressors to clean it out which really do a good job. If you open your case in warm weather months, to keep it cool, than make sure you blow it out more often. Dust and smoke are not good for a PC.

Just a little tip.

Tim