Another thing I want to add is Lucas' excuses for doing that, and how silly they are. You know, the whole, "Darth Vader was no longer Anakin" thing. DUMB! It makes MORE sense for Shaw to be at the end because it shows that as Vader was aging, so was his good, human side and that is how Luke was able to help him redeem himself. The whole, "...there is still good in you..." thing.

Or we could just use the logical answer that says since Anakin was human and only part machine, his human side would age normally.

No matter, it is hands down one of the dumbest changes in all of the SEs.