Like i said earlier, if it shortened the life to under 100k, I wouldnt touch it(or change car at 70k).
OTOH if its around 200k then itll prolly need rings and other misc stuff too (using that logic, using petrol shortens its life too).
It also depends on how long you keep the car, if you dont plan on having it for a long time why spend the extra money on petrol?