How do they decide which plane flies which route? I'm not looking for trade secrets here but say a plane finishes its cycle and gets back to Dubai, does it have xx amount of time on the ground before it is used again or are they cleaned up straight away and sent out same day?

Say a 777-300 ER has done LAX-DXB non stop, would they send it to do DXB-SYD or would it have a rest? I know it's metal and doesn't have a brain, I'm just wondering if they have a longer rest after a 14 hour flight.