Being in the reality of cruising it always comes down to the wife wanting the perfect filter. We were onboard for eight months so the under sink filter lasted about four of those months even though we had commissioned the tanks well before we left. We now have a list of marinas from Maine to Miami that we can get into and fill up with municipal water. So we're able to get to the destinations, so now how to top off our tanks. At one point we anchored out for a month or more so we had time to do the "What if" questions and water was often brought up.I'm gonna take this back to the beginning, and ask All U Get, the original poster, what is the goal of your filter? If you wife complains that the water out of the tanks tastes "icky" I bet you could get by with an activated charcoal filter such as a Brita.
There are places we wanted to stay that didn't have water where we could get to it and I'm sure many others once we jump to the islands. I've considered separating the two water tanks to keep potable in one which would make sense with a R/O system. Then we could store/pitch the jerry cans. There was no mention about how to winterize a R/O system, just a thought. There is a bit to consider as far as space requirements and energy use that we need to consider also. No simple answer but what we're looking at.
All U Get