When doing network upgrades and fixes, we need to assess whether a particular fix is relevant to exchange or pool operators. If it is, we need to notify them of the required version. We send them a message containing the reason for the upgrade and the version they need to upgrade to. The version details on GitHub should contain all the information required for upgrading.
When a release contains a critical undisclosed security vulnerability, we give two weeks' private notice about the fix and why it's required before we publicly announce the bug and the fix.
When a release contains a hard fork with network consensus changes, we need to give 2 months' notice to ensure every node is upgraded by the time the fork block height is reached.