I've been in the I.T. business for a good few years, here's some nuggets of advice:
You cannot ever be sure of 100% reliability; you can, however, make it less likely to lose data.
Firstly, you must have at least 2 copies of any data.
Ideally, you want a third copy of the data in a different place.
Backing-up must be easy to do, otherwise you'll never do it.
A RAID system is not for backing up data, whatever you may read elsewhere.
The life of CD's, is well preserved, is not so bad; but if you 1000's of CD's hanging around you WILL lose data from them.
For me, the best and easiest solution is multiple hard drives, and to upgrade them every year or so. Since the storage and price of hard drives is always falling, the cost is small. A 1TB H/D will hold more than 1000 GD shows in lossless format!
One more thing - you should power up an unused hard-drive once a year just to keep it ticking over.
The problem of how you play from the hard drive is a different matter though