Background activity setup - bg stops after two minutes - by: tonix

I'm here again trying to make the "internalcron working".
I've yet version 5.5.4, so I don't know if this feature changed a lot on next versions (I'm planning to migrate nextly).

When I configure my IMAP connection for reading emails, and then I start the background activity, the background task works for a couple of minutes, than the background activity status turns back to stopped.

Which is the principle for which this feature should work without stopping h24, of course without putting the PHP execution limits to weeks?
What am I missing? Should an admin be always logged?

Thanks,

Tonino