I had a NAS made by D-Link. The thing stopped working and I was worried that I'd never see my data again. Fortunately I was able to connect the drives to an older PC I had kicking around and accessed the data. It wasn't an obvious solution though and required posting on several forums before I found a document that discussed how to do it.

So instead of a proprietary device that's subject to being orphaned I today use that same PC running Linux and the ZFS file system to provide RAID redundancy for my data. All the parts are off-the-shelf and there's plenty of support to be found on-line.

A NAS is attractive because it's touted as a plug'n'play solution, but they are 1. proprietary, and 2. not cheap especially if you want to connect more than a couple drives. You can do better.