I purchased a Spectrapure MaxCap for my new house. I'm moving at the end of the month, so I don't have it up and running yet. I'm just wondering how often, on average, I will have to swap out the filters. I have the flush kit for the RO resin. I'm just looking for a ballpark estimate. I live in Canada, and it's much cheaper for me to have the replacement filters shipped to a PO box I keep in Niagara Falls, NY. As a result, I need to plan ahead a bit more than if I just had them delivered to my house. Also, do any of the filters have a "shelf life" if they aren't actually in use? If not, I may just order more than one at a time and store them at home.