On the whole, I was not panning around that long before it crashed. More than a few minutes. Not sure if it was 30 minutes. I had panned and switched to a different program, and it crashed while getting the tiles in the background.
I was not zooming at the time it crashed, and hadn't zoomed for some time. It was primarily panning across the state of AZ to pick up the tiles. Was not switching modes (topo/aerial) at all.
I resumed the panning after restarting the program and was able to finish AZ. I would guess my use after the crash was perhaps 5 times the use before it crashed. The previous crash was also in a relatively short time after starting the program. In neither case was the map.dat file very big (all the tiles were in one file, < 650MB).