In south central PA it varies a lot from one year to the next. Once the weather starts calling for consistent daytime temps of high 50s or better, I shut down. Some years that's early March, others it's mid to late April. On average, I'd say first or second week of April.
Being my first spring with the DS I want to see how well I can throttle it back when we're getting 50+ days but still chilly nights. I can't restart it in an hour like I could with the old stove, so I probably won't be shutting down and restarting if we get a short warm spell.
My coal use from here on out will determine next year's coal order. Starting the season with 2 tons for my old stove let me burn from early November to early April if need be. But the DS has burned 40-50 pounds a day during the coldest temps, so 2 tons won't get me through a whole season. This year's two ton pile went down fast the last 6 weeks.
About window-stats...on warm spring days, we have to do this in the room above the stove. The rest of the house is usually cooler. I'd rather lose a little heat from one room during the afternoon than shut down the stove, then have to run the heat pump a couple weeks. Not to mention the electric baseboard toasters in our basement room.