My water pump was replaced @ FOT in '21, but they did not replace the filter, it looks like it was replaced in 2018 before I bought the coach. How often does this filter need to be changed?
Very dependent on what coolant you have in there.
Do you know the type/brand/product and its age?
It's green, they replaced some when my water pump was replaced. Not sure the brand, probably could call them tomorrow to find out
When you find out probably to good idea to carry a couple of gallons.
Please do that and let us know exactly what was used.
That way we can give you accurate advice.