Quote Originally Posted by Tanooki View Post
The physical copy you can keep until the day you die. The digital rental(download) you can keep until the hardware breaks, because eventually they won't host the files on a server anymore and you're out a purchase then.
Just because you have a physical copy of something doesn't mean it will continue to work. There are plenty of dead cartridges and CD-Roms in the world and frankly, having multiple digital copies of something is probably a much safer approach to preservation long-term.