4 years ?, I thought I was pushing it waiting over two years to change ours. Would never have admitted on the forum as to waiting two years until now.
I waited so long in hopes of putting one of those fancy water separators that a friend showed me on his cummins onto our wagons.

At least you had the parts and tools prepared ahead of time. I wondered how long a person should wait to change their fuel filter. I only changed ours cause of the time it had been on there.... otherwise no performance loss with the old filter and no gain with the new one.
I guess you established a maximum period they will work until. Maybe the water froze in combination with the rust and caused the cracks?