I might add that aside from the occasional up-sizing when doing geometric alterations, I try to keep the file size as is as long as possible. While I work up images as Tiffs, I want the ability to go back to the raw file easily. I also usually don't sharpen until the very end of my processing.
Additionally, while my current favorite camera (Sony a7r) has sufficient pixels (36 mp) for most uses, I sometimes up-res, particularly older files, to 360 or 720 for my "print only" file, which is usually deleted after the print is complete. I suspect PS CC does a better job of up-sizing than the print drivers, though I admit I have not actually tested it. (My actual best guess is that no one would ever see the difference, but it makes me feel better!)
Paul