I do not think they re-record greatest Hits albums.
I think they just get the pre-recorded songs from previous albums and compile them in to one great ultimate mega awesome album!

And that wont take very long at all.

Also I went back and started to watch season one again.
In the caves while Locke and Charlie are alone they talk about Drive Shaft. Locke was a great Fan.
He said he owned BOTH their albums, but Charlie really broke away with his solo work.
So that mean DS had two albums and Charlie had a solo one.
Three albums is plenty to make a greatest hits album.