There is nothing in your post that suggest he isn't doing a great job or getting a ton done. Assuming there isn't a problem with performance - perhaps he enjoy

There is nothing in your post that suggest he isn't doing a great job or getting a ton done. Assuming there isn't a problem with performance - perhaps he enjoys working half of his hours when you are not there. So he can productively get through code without constant startup issues. I mean this with no disregard to the importance of things other than coding - but from experience these issues can make it tough to stay on schedule and get through the mountains of coding necessary. A schedule like his could balance these items out.