Let's say you're going to be gone 1-2 nights, you might not need to run the generator at all.
This assumes the following:
You have the TT hooked up to 115V at home (or at storage) and the batteries are fully charged when you leave.  
You have 2 batteries rather than just one.  
You have LED lights, or will be careful with how much you use the lights
You don't need the furnace to run more than a few times through each night.
You will be hooking your TT back up to 115V when you get home.
I still take our generator with us on most dry camping weekends, but I rarely run it now that I know what we're capable of.  It's similar to learning how well we can manage our fresh/gray/black tanks without hookups.