When moving to Biodiesel the old crud will be cleaned from the fuel tank and fuel lines.  After 160,000 miles on normal diesel I was expecting massive filter blockages so I bought 4 FRAM PS586 filters for £14.
The total time to replace a filter was under 10 minutes.
To gauge the condition I decided to cut them open and look at the element.

This is what a fuel filter looks like after 10,000 miles on dinodiesel.

This is what a fuel filter looks like after 500 miles on biodiesel

After a further 1000 miles this is the condition.

The first 500 miles of Biodiesel released as much crud as 10,000 miles on dinodiesel, this filter would probably last until my normal 10,000 mile change but out of interest I changed it.

I'm going to cut the next one up in 8000 miles (putting it back to my original service interval)
All in all I think this was worth while as I know the state of my fuel system for very little time and expense.