I do it all!!! I can run around the mainline loop while switching the industries inside the mainline loop. If there were 2 of me I could even move engines around at the engine facility while doing the other 2.
I have gotten fond of letting my short, 5-6 car passenger trains run the main while I watch them go, but then I getting thinking about extending the mainline around the entire upstairs space!!!
Here's my simple around the wall plan:
I've found I have a bow in the drop down bridge where the Wye is located. It's made of plywood and I'm thinking of getting a 1/8" or 1/4" x 12" x 38" aluminum plate to replace it with and some aluminum angle to keep it rigid.
This was 3-rail converted to 2-rail by removing the middle rail. All engines running on this are battery-powered, remote-control, NO wiring to the layout!
I still have 4 TMCC and 2 PS2 engines, but I have to put down a circle of track to run them. Those will probably end up going to the 2 grandsons.
I even have a Bachmann G-scale 4-6-0 that I converted to BPRC and run that whenever I get the urge and can find a spot for the track. A 12v, 2000Mah NiMh battery pack is plenty of power for the engine, tankcar, flatcar, and caboose.
So I say...Run em if you got em!!!