It depends heavily on just how snowed in we are this winter...
Usually the car gets filled about once a week with 6-8 gallons. I don't like to run it below half a tank (we live in a rural area), so I'll fill it when I'm out if it's below 5/8ths. I'm planning on replacing most of these miles with a Leaf at some point, once their prices drop enough. Model 3 & Bolt should nicely crater used Leaf prices...
The truck varies wildly. Sometimes I'll fill it twice a month, other times it goes long enough that I have to remember to put winterizer in the rear tank before it gets cold. I'd say it gets filled every 2 months on average, for about $40 (I usually run the front tank down, and a few gallons out of the rear, then refill it). It gets used when we need a truck for something, or a six passenger vehicle. Or, recently, because the car can't get out of the driveway.