The newer black elements are supposed to have a different better filter material with a better water rejection component that isn't supposed to deteriorate over time. Don't think they list a life expectancy in fuel though.
As a practice, I run the element for a year then switch to the other and replace the used one. So, the element sits for a year and then is used for a year. Being that I'm OCD, 2 or 3 times a year, I will switch to the alternate filter element for 15 minutes to flush the fuel out so that the fuel doesn't sit in the filter for a year. I know, totally OCD. But it's easy to do and gives me peace of mind.
Ted