Great post Tglazie! Well written.
Now for my 5 cents - my 4 year old Sulcata started digging her burrow about 2 months ago and it's now 10 feet deep. I'm very proud of her..ha ha.
I actually prefer that my sulcatas burrow since they can thermoregulate their temps better when it's up and over 110 degrees here in AZ.

Keep in my that MOST Sulcatas burrow down to regulate their temps, they generally do not burrow down 10 feet deep, over and under your neighbors yard and back up again. The burrows will go down and sometimes to the side but they usually don't come back up again, they have their one entrance/exit hole.