Microsoft has pledged ten years of support for Windows 10 on the desktop, but the mobile version may not live so long. Those updates may not be distributed quite like Microsoft previously said, either. The company has updated its Support Lifecycle page for the most recent version of its phone OS. The devil is in the details, and those details may not line up with Microsoft's previous statements.
Windows 10 Mobile will get "a minimum of 24 months" of security updates. The company says those updates will be incremental, so users will need to install previous updates in order to get the latest. Each of those updates will be mandatory to receive support, too. Mainstream support is currently scheduled to end on January 9, 2018 for both consumers and businesses.
In the past, Microsoft had said that it would control Windows 10 Mobile updates itself, but the Support Lifecycle page indicates that may not always be the case. Instead, Microsoft notes that the distribution of updates "may be controlled by the mobile operator or the phone manufacturer from which you purchased your phone." Windows Phone 8.1 updates were already controlled by carriers, much like Android updates on non-Nexus devices.