Have you got some old backups living on DVDs? It's time to upgrade them for real long-term reliability.
The one big problem that people are just beginning to face is the lifespan of DVD backups. DVDs have been great, thanks to a good few gigabytes of storage on a single disc. But a lot of people have now filed them away, like they're a good long term storage option.
Depending on your discs, you shouldn't feel confident of more than 30 years, and as little as 5 years with a bad disc.
If you have CDs or DVDs with important data on them, tucked away for long term storage, then it is time to get them out and move that data to a better place. Unless you have purchased expensive long-term, archival-quality discs that guarantee lifespan, these are going to rot and lose your data.
Right now, cloud storage or redundant local storage on active hard drives are much better backup options.
And, as ever, never keep one copy. Even with archival grade storage, always keep at least two. Even then, I'd move those precious archives around now and then, to be really, really sure.