If you run synthetic, they will be leaking badly by 70-80k. If you run non-synthetic and extended drain intervals, they may never leak. But your engine will be done by 200k.
GD, can you explain why this is? Why different oils cause such bigger issues?
I don't know what oil was used in the past, so, I'm not sure what to use.
I have purchased all new Subaru parts for timing belt area, to include New Oil Pump (if the one that is on there has a 7 or 9 on the case), New Water Pump, Thermostat, all the idler & tensioner pulleys, coolant sensor, Thermostat and hoses and radiator...