When to stop working on a PCB layout
You usually don't pay for vias if the density is reasonable and the quantities are not astronomical. 

Vias don't make much difference unless your edges are less than a nanosecond or two, for your frequencies forget about it. 

You're done. Maybe you need a deadline.. .

P.S. Sometimes it's better to let the layout sit for a few days and then come back to the schematic and really look it, and then the layout. Modern EDA tools usually make sure the layout matches the schematic, but sometimes what you put in the schematic isn't what you thought you put there.