I have one runtime broken up with the sub folder routine, I don't have any speed issues except on initial launch.
I find, and I'm not alone in this, that the workflow is easier using sub folders and accessing my entire runtime list using the little black arrow at the right hand side, nothing could be easier and yes I have tried multiple runtimes and it doesn't do it for me!

But it's an old discussion that we don't need to start again, some prefer multiples, others single, each to his own!  And don't try to convert me 'cos you won't! 

Injustice will be avenged.
Cofiwch Dryweryn.