This mod informs you in the chat when the last active ECM is about to stop working.

Install this mod to get access to the settings menu
https://modworkshop.net/mydownloads.php?action=view_down&did=25274

OR
You can open 'ecmjammerbase.lua' with a text editor to configure the mod. You can change the time, the message and the recipients of the message (just you or everyone).