Let me clear this up a bit. I was talking about "Fixing" a track...by punching in over the bad parts. I use the auto punch in feature, which allows me to pick precisley where to punch in and out.
I have also used two or more tracks and sub-mixed the best of each track down to a third track. This is useful when you have a guest musician/vocalist in the studio, and you want to get the most out of the time that they are there. Later on "Off the clock" you can audition each track, and pick the best parts...(Verse, chorus, bridge etc.) to use as the final take. I believe this is called "Comping tracks" and is often used by the big guys as a way to save time and money.
Of course you have to have enough empty tracks to do this. However, THIS IS NOT CALLED PUNCHING IN.
Sincerely;
Dom Franco