I always have the summer tires on.
But I only drive my z once every 2 weeks in the winter...
I am from Mass too. I'd say wait till April. This year we got a lot of snow here and I am sure there will be more(maybe not the big ones but still)...
I had aweful experience driving a RWD in the winter with summer tires on. Not that I didn't survive in the storm. But the worst was after the storm in the parking lot. I couldn't even backup from the parking spot and my G35 coupe was stuck there for 1 and half month until the snow/ice around the car melted... My suggestion is wait till April. But a better plan is to have 2 sets of wheels - one for winter one for summer. So that time like now, you can just easily to switch them out.