My longest distance covered was the outbound on
this trip, 950nm or so. 6hrs 10mins. The longest in duration was the return flight which was shorter but was 6hrs 50mins. That flight duration was matched on the outbound flight
here.
In Europe, especially in southern Europe, the limiting factor is more often the availability of alternates which have avgas, rather than some precise calculation using the aircraft range, the flight to the alternate, and legal reserves. In Europe, I regard the FAA 45 mins IFR reserve as much too thin - even if you have an accurate fuel totaliser which the vast majority of pilots don't have.
The TB20 will do about 1300nm to zero fuel, ISA, MTOW, still air.