I change mine every 7 days or earlier if they start to overflow.  I can tell as my skimmer starts going nuts.  I don't bother turning them inside out as I didn't really see them getting any cleaner when I did.  I have about 10 that I cycle in and out and do 1 load of laundry every couple of months.  No bleach or detergent. 
 
I also have a quick look in the sock to make sure I didn't lose any starfish, snails, etc 
		
	
		
		
		
		
			
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				So many ideas, so little money!
			 
		
		
		
		
	
		
		
	
	
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