Anybody have anything definitive for how many head firings the heads of an SP-540V are good for?  My tech told me around 5 billion.  I'm above that on one head and below it on the other, but the machine is printing fine.  I've only had the machine 11 months so far, and don't think that I print all that much.  Comments?
	
		
			
		
		
	
			
			 
				