Re: Fuel/water separator change?? When
A filter will last anywhere from 10 minutes to 5 years, depending on the amount of "stuff" you have in your fuel. Changing the filter a time based schedule is no better than changing the oil in your car every 90 days if you drive it or not.
The only real way to determine the useful life of a filter is to monitor vacuum required to pull the fuel thru the filter. I use a simple, screw in vacuum monitor that screws into the extra port on the filter base and lets me know when the filter is starting to see some restriction. With filters running $25-30 each, the monitor has paid for itself many times over since I installed it 5 years ago.
What I’ve found in the past 5 years is that filters start to rust out (~ 2 years) long before they need changed for performance purposes.