Back to back mid and long run

Noticing in all my plans (I use Run with Hal) that fridays I usually have my mid run (7-9 miles) followed by my long runs (13-20 miles) on saturdays. Is there a benefit to this? Training to run on tired legs? I’m very comfortable running and training for half marathons but this is my first full training block and it’s getting harder to end my weeks with this much back to back running. Don’t get me wrong… I will get it done no matter what. I “get” to run and truly love that my body and mind allows me to do this.