4 years... only 4 years. Their software is capable of being used for decades. This is just sad.
But if Microsoft support it for decades then how are they going to force your employer to buy new licenses?
A specific version of their software was supported for 4 years. There are newer versions readily available. I think 4 years support for a product like this, while there are far newer versions is really good.
I still use my Office 2010 for Windows. Their official support will only end this year. That's quite value for money to me.