Winter camping, advice on staying warm in camp?

I've been doing some winter camping (car camping, not backpacking).

Temperatures have been as low as 15 degrees F (-9.5 C), but more usually in the 20's F.

I have been quite warm in the tent. I toss a blanket on top of my sleeping bag and no issues.

Staying warm when up and about in camp has been a real challenge. I am snowshoeing or actively cooking, it's not a problem. But there's a lot of down time in camp and I am freezing. It's tempting to just crawl into bed the minute it gets dark.

Wondering what advice you have, at a certain point bundling up with more layers is not really helping.