The release notes document is not guaranteed to reflect the version deployed in perfect time sync.
While we try to publish it as close as possible it's not always in sync, and is not considered a tool to get notified when a tenant is expected to be upgraded (the upgrade is gradual and can sometimes take days).
Currently, there is no built in monitor available to tell you when a new version started deployment for your tenant (which will kick start the 72 hours clock).
What most customers do is set a few machines without delays, and in the rare condition that something breaks they have time to respond.
I am aware of some customers implementing their own monitor which scans the sensor deployment folder or service for the current version, and notifies them the minute they see the sensor changed version number...