If you've ever heard the grinding of your computer's
First off, optical storage offers a level of durability that maybe only a N64 cartridge could beat. Optical storage, compared to that of hard drive storage, is much less susceptible to shock damage, and can endure a larger variance in temperature, humidity, and exposure to foreign particulates. Hard drives are a useful computer implement, but they can be ruined by things like magnetic fluctuations, humidity, and even tiny bits of dust inside the platter's drive case. Hard disk drives are manufactured in clean rooms and filled with a filtered gas to prevent any contamination. Optical disks, on the other hand, can be saved, stored, transferred, etc. with a minimal amount of stress on the disk or on its contained data.
So what about long term viability? Well, optical comes out the clear winner here. The average optical disk is capable of storing data for much long periods of time. Provided an optical disk is taken care of, data remains readable in excess of fifty years later. Magnetic storage, over the long term, suffers degradation due to the mechanism of its storage. Should the drive function long enough, data on a drive degrades over time unless it is rewritten and maintained. Thus, optical media is a better choice if you're looking for a longer term solution.
There are clear advantages to traditional magnetic storage. Magnetic media does offer the ability to overwrite and change data, which is why it is the primary and most popular form of computer storage. However, optical media is more affordable on a per-unit basis of storage, and in long term storage applications, provides a much more cost effective solution. Even in terms of highly reliable Cloud storage solutions, the monthly cost of devoted Cloud storage can quickly outweigh that of optical media. This isn't to say that optical storage is for everyone: if you have multiple layers of redundancy already, or are looking for a very high capacity solution, then you might be comfortable with multiple drives.