I run the larger 7" diameter by 16" long sock and change it once a week. Can last up to about 10 days if I want. The smaller 4" inch socks that most people use, need to be cleaned far more often.

I posted this poll last week. Hope it answers your question as it did mine.

http://www.canreef.com/vbulletin/showthread.php?t=94604