The worse mileage your car gets the more you can save by driving correctly.
My daughter has an Expedition with the 4.6, a towing package and a factory mpg readout.. She routinely gets 11.5 mpg average and never uses the mpg readout.. Just by paying attention to the readout when driving and practicing some basic hypermiling techniques I can get about 17 mpg under the same conditions.
If your car(s) are 1996 or later, get a Scangauge, that will help you more than anything.
Welcome. For the Suburban, what year and engine? I'm currently getting 17 from my 2002 Sierra 4x4 5.3.
Do you put on a lot of non-trucking miles? If so, gas and maintenance savings might easily pay for a more efficient vehicle to use when you don't need a truck, while still allowing you to keep the trucks for when you do.