How long does a business phone system last?

It of course depends on the needed features, state of phones, and overall reliability of the system, but businesses often replace their phone systems every 10 years or so. With the right maintenance you can create a replacement cycle so that you never have to replace your entire system all at once unless you're in need of new features such as video calling or are making the switch from an analog system to VoIP (which is much cheaper monthly).