Years ago two friesians finished in a 40 km(or so) endurance ride.
After that I never heard of Friesians again in endurance. They
definitely did not compete in the last few years in endurance rides
in Holland. And we have a lot of Friesians here (I live just a few
kilometers from Friesland).
In my experience they are hard to get in a reasonable condition, they
are not fast, they don't perform well in warm weather, but I,m sure
they can do short distances.
Have you got one?
Jeike