You know you can back it up yourself, use a DVD, USB thumb drive or hard drive (preferably disc, in a nice case).
You pay for the convenience of them keeping a backup for you, or back it up yourself. If the 5 bucks is gonna break the deal for you, the sub 1/4 of a dollar dvd shouldn't.
I mean your other options, if you still want to play the game, is to buy a retail version or from a different DD service that operates a service allowing you "unlimited downloads*" (and charge premium prices for anything not on sale). Either way you go, you're gonna be paying more if you don't want to go this route and back it up yourself.
* = unlimited unless they go out of business
You should always back up everything you download and desire to keep around anyway. I've got all of my Steam, Impulse, D2D,& EA Store games backed up on an external HDD that also backs up all my media purchases from Zune, Amazon & iTunes. Once a month I make sure to stay current. The drive could fail though, so I really should put these on DVD's or a 2nd hard drive.
Speaking of media, I can't re-download my Amazon/iTunes media again. And they don't even offer a service I know about to let you.