As an update, I did the double batch brew yesterday. The actual mash/brew went well. The biggest hiccup was that I had misplaced my digital thermometer and spent about an hour cussing and searching my house before I found it and could get started (Note to self -- prepare everything for brew days the night before).
The whole process took me 8 hours from dough in to both beers being in fermenters and my equipment soaking in PBW. The reason it took so long was that I decided to try a modified triple decoction mash (doughed in at 133, stepped to 145, stepped to 155, mashed out). I was not done with the sparge until close to 5 hours in. I also tweaked my boil approach slightly. After the first beer had been boiling for about 30 minutes on the outside burner, I transferred it to my stovetop to finish the boil. At that point, I stared heating the second batch on the outside burner, which is stronger. Both beers finished with OGs within .002 of targets, so I am hopeful.
Between the double batch and the triple decoction, I definitely did no have much free time during the day. Luckily, my wife was around and willing to run downstairs from time to time to fill my pint glass and get various brewing implements.