Since commands run on shared servers, it is important that long-running scripts are being actively monitored by the users who started them. This is an objective of the shorter 15-second time limit. A future paid subscription option may include the ability to run commands for longer without supervision.

15 seconds is very short. Could it be 60 seconds with the "Add 60 seconds" appearing at 20s to go so that it matters less if you loose concentration?

With the "Add 15 Seconds" button, you can effectively give your commands infinite running time if you continue clicking the button until the command is finished.

Increase time limit is important. It is not an equivalent for Matlab with time limits.