When I bought my custom frame I was told by the person working that it's not good to keep them in the tube for an extended period of time. I mean, she made it sound like it was a good thing I'd brought it in basically the day after receiving it! She said that it can cause the print to permanently stay rolled...well, you know what I mean. Like, if you buy a poster from the store that comes all rolled up, if you unroll it, it'll still roll itself back up. That type of thing.
So she said that it's best to get it out of the tube ASAP. I know a few fellow Freaks have picked up some portfolios to hold their prints in until they get around to framing them, as they keep them flat and protected! Zod mentioned what kind he bought a dozen or so pages back...look for when this thread had some Daredevil print pictures, and you'll find his post about portfolios shortly after, I believe!
I'd say that's the best and cheapest option to keep them protected until you get around to framing them! Or if you just want to keep them in there like he does, then that'll work too!