Your files are stored on the NAS server and can be synchronized, or automatically kept up-to-date, on all of your devices. This service needs to always be online so the NAS should always be on. If you are using your NAS for web hosting like I am, you need to keep it online 24/7.
Really, a NAS is not quite like a washing machine, that you can hold onto for as long as it works; a NAS is more like a time machine. My recommendation is to change your NAS every 5 YEARS. Most NAS devices have a 3-year warranty.
