...
If the checkout is not possible (for example, the remainder of available licenses have been checked out in the meantime), this information will be relayed to the application, which will behave in the manner specified. If, for example, five heartbeats in a row fail, automatic heartbeats will call an exit() function on behalf of the application and print error information to the screen. This behavior can be overridden with the HEARTBEAT_EXIT_FUNCTION callback, described in Heartbeats.
Using a counter to prevent license overuse
When the server is restarted it takes a few minutes for all clients to reconnect. Particularly for applications that run for short periods of time, license overuse may occur if the license server is stopped and restarted frequently.
...