Mark Chance
Boingy! Boingy!
In the past, about a dozen years ago, I was able to prep for and DM three sessions of D&D (2E back then) per week, with at least two hours per session. Prep took me about an hour per session...
If not getting out of the DMing business is a good fix, you could try not prepping so much. A prep hours to session hours ratio of 1 to 2 seems awfully high to me, no matter what game system we're talking about.
Shoot for something more like a 1 to 4 ratio and then do something relaxing with the extra time. I like to read and drink whiskey, for example.
Prep one-page dungeons and just wing the rest.