With less then 400 hours on it I've changed it twice when it was jelled up in the winter. So I'm keeping pace with the once per year or 500hrs recommended in the owners manual.
I probably don't change nearly as often as most people.
I have two diesel tanks. One for the road trucks and another for the tractors. Both have fuel filter/water separator units at the pump. I keep the filters on the pumps changed, and just don't have much problem with the truck and tractor filters.
Much depends on the quality of the fuel you get . I always buy from the same source and have never had a problem . I have a 2006 M5700 and have never had to change the fuel filter , but then again it has less than 600 hrs. on it . I will change it this summer though .
I've made it a habit to change every fall B4 snow season and drain any grunge from the tank as I've been caught when it is just too darn cold.
That is also when I do my major maintenance like lubes, air filter and a thorough grease job.
Every fuel up I drain a bit of fuel 'just in case' and occasionally get a bit water or grunge.
As A pilot we'd drain B4 every flight an ounce to check for H2O so I have that habit ingrained.
You can do it whenever you feel like it, but pushing it 300 hours sounds just a wee bit too long for me. Those things have a nasty habit of stopping up on you at the worst possible times. I hope you at least have a new one on hand, just in case.