I know a guy who bought a 33 at auction. It was in pretty rough shape, no service history, high kilometers etc. He got it registered and went straight to doing 7k pulls, clutch kicks and general abuse all the time - with no oil change or servicing at all. Oh and of course boost wound way up with no tune etc.
When my mate first saw the car he pulled out the dipstick and was shocked to see less than 2mm of tar-like burnt oil showing (after being wiped clean). 2 months go by of absolute torture and the engine finally starts blowing oil out the dipstick (blow-by). Still the car ran longer than that, with probably less than 2 liters of old, burnt oil in it. It finally succumbed a few weeks later.
A testament to the RB series' durability. BUT PLEASE SERVICE IT FREQUENTLY ANYWAY