The Janitor visits me far more frequently when I set a 'You've spent an hour on this, hon' timer for a difficult problem. At which point it's time for me to go

The Janitor visits me far more frequently when I set a 'You've spent an hour on this, hon' timer for a difficult problem. At which point it's time for me to go take a break, talk to other people, have a cup of tea. Then come back - take a brief look at the original problem - and then, if nothing occurs, to work on a related problem before coming back to it and seeing if I can make any more progress. Maybe it's just me, but protracted work on something I don't feel I'm making progress on seems to stop me thinking.