Similar to a question just asked, but i think it's different enough...
I have a two-zone forced-hot-water heating system, where each floor is its own zone. The zones are connected by an open stairwell.
It seems reasonable to me to set the downstairs back farther at night than upstairs, keeping the upstairs bedrooms a bit warmer.
The question is, given convection in that stairwell, does it really make sense to let the upstairs setting drop below downstairs during the day, or would I need to isolate that stairwell (or at least close all the upstairs doors) for this to really save energy?