Background activity setup - bg stops after two minutes

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

Of course php is not permitted to set itself for infinite loop. This is a normal safety precaution.
Wouldn't it be easier to provide a cron php file to execute when needed?
Maybe a simple cron php file which will call already existing functions for polling IMAP, importing files, etc...

(real) cron is the only affordable solution, just need two lines of comment and it's done. Windows users may use actual scheduler as alternative, but I feel they will prefer schtasks.
It should not be so difficult to extract one or two files to put be in cron, but it would save time and nightmares to the most of users.