What to do to make good use of long stretches of cloudy nights?
Dark frames! With a temperature-regulated camera, one dark frame at a given temperature (and exposure) is as good as another. So I spend overcast evenings collecting dark frames at different exposure lengths and binnings, all at the temperature I use at this time of year (-20°C). To start with I collect 32 of each of the types I use, and pre-combine them into Master Dark frames using CCDStack. If it remains cloudy even longer, I also start collecting darks at a warmer temperature (-10°C) for use when the weather warms up.