Steve -
We thought the TB41 was the right size for us and didn't think for 2 people we needed the extra space in the TB51.
We probably grocery shopped every 4-6 days. Used the truckfridge mostly for fruit & vegs, dairy, cold cuts, hummus, and cold drinks. It also came in very handy for leftovers especially when cooking dinners in the thermal cooker.
It's hard to imagine how much more pleasant camping and travelling is when you don't have to deal with ice.
This summer we're planning a trip to Glacier Nat'l. Park and the Canadian Rockies, and you'll be sure we'll be taking the TB41 again.