I also got bored easily. So I do multiple games, but before I change games I sometimes do 1 route or 2 routes. But somehow if I get immersive on the game I'll finish it right off.
With regards towards the unfinished games. I do go back to them then finish one route then leave it behnd until i got the courage to play it again. I think for me i do this so that the plot would reset in my mind if i go another ml route. And I can enjoy thinking about the route i just recently finished. Something like that.