Wow, very enlightening. I have been lucky then. I am in a similar boat as the OP, as I haven't "had" to reinstall in about 2 years - the current lifetime of this laptop. Should I have well is another story I suppose. I am seeing that I could probably benefit from a fresh install.
Not to "hijack" this thread but it does seem to be on-topic ( to me anyway ):
Since most of you are reinstalling fairly often (monthly, bi-monthly, etc), how are you doing your backups ? Are you ? If so, how ? Seems very important if you are going to reinstall everything.