I have spent hours and hours reading about this topic. My brother also has built houses, coops, garages, and other buildings professionally. Based on reading and advice...if you live where there is snow, you need to be sure your building can handle it. 16 inches on center is the standard. It's what I went with and what I recommend for you given your location.
Could you go with more space between, sure, but why risk it to save 2 boards.
I did full size headers for windows and doors even though most plans call for 2x4s set flat. I don't want to risk it. A March time, 2ft, heavy, wet, snowfall wieghs a lot and we get those yearly.