When a new official update is ready, eM Client will offer you an 'Automatic update' next time you run it. We recommend installing the update but if you don't have the time and would prefer to install it later, you can click the 'Later' button and choose to postpone the update for 1 Day, 2 Days, 3 Days, 1 Week or 1 Month. If you click the X button in the top right, the Update will not be installed and the window will pop up on the next startup.

You will never receive an update prompt that your activated license is not valid for, but if you'd rather just use an older version indefinitely and don't want to reject updates every month, there can be a manual update limit set on your license and activation.
Pro license users can set this limit (called "Set version") via the License Manager. Just open your Licenses or Activations tab and click Set version for your license. Select the version you want to use from the list and save this setting.
Free license users can send a request for an update limit to info@emclient.com