not here in oz you don't! no credit for the miles, no completion prize.
if you withdraw (as opposed to vet out) you basically end up as if you
never entered.
the only exception is an elevator ride. these are rides greater than 80km
(50miles) where you complete the 80km then decide whether or not to
elevate to the final distance (usually 110km or more - up to 200km over
two days that i know of). if you stop at the 80km mark you get credited
for it (distance and completion prize), but if you go on and vet out you
lose it.
do you guys have elevator rides in your countries?
nik & the gang (taaj, saki & dippa) from australia