It seems that this is a touchy subject, and I've seen it discussed before.
The majority of what I'm hearing is that it's not important, with one or two people saying they clean them occasionally (once / twice a year)
If there's no additional input that isn't an argument, I think the thread has served it's purpose. Thank you to everyone that answered. It gave me some things to think about.
I think that's the best way for this to end, if I have offended fredg in any way it was not an intent. I will be taking a break from TF forums for a while, a few have spoiled the bunch as its said.