[wraith]

Dont look to far away from the actual rebuild as the culprit. All of the issues with oil returning to the pan, viscosity etc., were designed when you biught the car by Mitsubishi to provide a long healthy life. If your pushing the engine way outside of operating range then some of these things might need addressing. However, you have not subjected it to huge power outputs and we assume it was never starved of oil, either during first startup or during the first 5000 miles. I hear many people on 3si suggest running heavier weight oils in these motors as a preventative measure, and I would argue that doing this may even accelerate engine deterioration, not extend its life.
I opted to just replace my short block with a new factory one to reduce down-time and remove incompetence from the picture, but if I knew of a reasonable shop that I could trust to do the work, I would have had a forged engine put in. Grooms sounds pretty reasonable for what they do. I would expect a good rebuild would survive at least as long as a typical stock motor. My original was still good at 117k miles when it was replaced and I never did anything in terms of maintenance but replace the oil pump when the 60k was done, and change the oil every 3000 miles with good synthetic at stock viscosity 10-30w.