<a href=showthread.php?s=&postid=14355385#post14355385 target=_blank>Originally posted</a> by DMBillies
I just did a big maintenance job on it this weekend.
When I said this, what I meant to say is I replaced every filter but the DI (which I have done 'fairly recently').
Honestly, it was the first RO change I ever did
And I have had that unit almost since joining the club. I'd have to check the date on it, but suffice it to say I've had it more than 2 years for certain and in those two years I've been working with tank volumes adding up to at least more than 180 gallons up to about 300 gallons. Aside from water changes, I was evaporating about 25+ gallons per week. Figuring a conversion of about 1 gallon RO/DI for each gallon of water put through, that's 100 gallons per week through the first phases of the filter or in the neighborhood of 10,000 gallons in 2 years just from evap.
I regularly replace my sediment and charcoal filters and if I notice my TDS of the RO output bumping up to 1 or 2 TDS (before the DI), I just change them because they are cheap (usually they have some visible evidence that they are getting old, particularly the sediment filter which starts to noticably color pretty quick... and I definitely change that most often). Usually, that knocks that number back down to 0. When I noticed it didn't and knowing how long the RO was in there, I figured I should change it out.
I am assuming that the first 3 filters and the RO are doing most of the heavy lifting because my DI has never shown anything but 0 TDS and its never changed colors (and yes, I have verified that TDS reading with other meters). I did replace it a while ago figuring it had to have run its lifecycle, but who knows if that is wasted money.
I'm living in an older house now, so I'm expecting to get more junk out of the pipes, but it certainly seems to me that filters may not need to be replaced as often as people think, especially if you stay on replacing the sediment (particularly) and charcoal filters. I would also guess that running them more often will extend RO life as opposed to having them sit and using the fast flush thing whenever you do let it sit. Because of how much water I make, mine never sits for more than a few days without water going through.
I use production to tell me when to replace my filters which I brought extra when I got my unit for under $100 at 
