For me, the amount of prep time I spend for a session depends on how far along the grand campaign I am. If I'm starting a new campaign for all new players, the prep time is considerable. I'm not a fan of using published modules, but I love injecting components from the ShadowWorld companions into my game world and that saves time. Length of prep also depends on how long that night's session will be. If I know my group is only dealing with a small town or a set of tasks that won't have them all over the place, prep time is again less. I haven't looked in depth at the data yet, did the numbers for prep time take those factors into consideration? Or the GM depth of knowledge of the system? My daughter wanted to try running her first session and it took us hours just prepping for her, where it would have taken me far less time to create the same scenario.
I can see the 5' grid being extremely helpful for online folks to use, particularly if the session ends for a week and picks up later. That visual is great to have to remind everyone where they were. We did that ourselves when we all gamed in house. We were fortunate to have the basement area that was undisturbed for the entire week and we could leave our pieces on the grid map.
I'm not surprised the game stores are dropping as a playing venue. I can't even tell you where the nearest gaming shop is for my town and the surround 3 towns. The one that was local to me closed down 2 years ago. I've seen shopping malls in other states (1-2 hours drive away) that have gaming stores now with more table then shelves of stock. That could be a trend on the upswing now; store fronts for actually playing the games vs. one that is meant to sell product and has a couple of tables in the back.
I must do forty to sixty hours of prep for those weekends and at the core of it is a bought adventure and a bought setting that I have converted to RM. Those conversions are part of the prep time but mostly it is developing the world and NPCs around where the characters are going and all the off piste places they could go.
Wow. Even knowing that you and your group game only 2-4 times per year, that's a lot of work. My hat off to you, sir. Do you run a complete campaign in each meeting, or do you have that one campaign over the course of the year?
... most groups prefer 5' gridded combat (by a ratio of more than 3 to 1) over the Theatre, even despite the way 5th edition has bent over backwards to promote Theatre combat.
We played 4e for quite a while, then the Beta for a good amount of time, then finally into 5e when it was released and we never even considered it being Theater of the Mind. I find that striking as you mention that one of the hopes was for 5e to move away from the grid. It just never occurred to us. Never mind that it wasn't an option the GM gave us, it was just never even a thought. I think at least 2 members of that group just never thought that it would be played without the grid map. I think when 2e (or around that time) was out, I was with a group who did all TotM for their sessions.