Normally I would say "do the minimum to keep the car running reliably", but I have been burned by the "new heads on an old bottom end" fix.
Yes the cylinders stay good, but I am not so sure the rings keep their spring. I do not know ring wear rate, but they do start at about 5 mm wide, and a from what I know of engineering mechanics, reducing that to 4 mm will reduce the pressure of the ring to the cylinder wall substantially. Math is one thing, molecular interface, material fatigue, and simple cracks another.
Testing cold static compression is a standard test, but I a waiting for a spark plug replacement test device (that I can afford) that measures hot combustion compression.
Blah blah, in short, new heads on an old shortblock often burn oil. Higher compression may also cause increased pressure on bottom end bearings
I for one do not think Subaru bottom ends are "bullet proof". They are aluminum. My experince says they are noisy and loose after 75k miles (nless babied, which I mostly do), and that owners just get used to the noise.
I would replace the whole thing with a rebuilt long block. I stand by my recommendation for this builder:.
Edited by uniberp, 17 February 2013 - 09:17 AM.