VIP fluid rotation

I own a VIP 200 as well. My lab is a Good Laboratory Practice (GLP) lab and our Standard Operating Procedures (SOP's) state that the fluids are rotated at approximately every 250 cassettes. That does not mean however, that we just put tissues on until we reach the 250 cassettes. The fluids are checked each time we run the processor and if needed fluids are changed. All of our tissues are received fixed so the first station on the VIP is 70% ethanol. When we reach the approx 250 cassettes the 70, 80% are dumped and replaced with new. The first 95% is also dumped and remainder 95% are rotated forward including the absolute ethanol and new added to the last.