Dont quote me on this, but I researched this same question about 4 years ago, and they told me that the chinese glass tubes have micro leaks, and will degrade with in time. I hope some one can once again clarify this.
All CO2 tubes lose efficacy over time - it's more to do with the gas settling to the point where it can't be sufficiently excited to generate a coherent laser. The cheap glass tubes will eventually outgas over time, but you're more likely to have gas settling problems before that becomes an issue.
You can kind of re-excite the gas in a laser by running it on full power for a short while before you start your actual job, but every time the gas settles like that, it loses some of its efficiency, and the laser gets progressively weaker.
So, short answer - no, don't store them. It's a great way of wasting your money.