Winter is 15 days. With a family of 6, you would need 90 food to survive winter. That means you need to add 3 food above and beyond what you use during every day of summer and autumn. Or in other words, you need to harvest 9 food every day or you will die.
Yes, not being able to get food except from the deep forest in winter would certainly make the food game much more important.
More importantly, since you can't gather food in the forest in winter, going into winter with not enough food means you know you will die. I see this as a frustration factor. If you know you are dead and there's nothing you can do about it, why continue playing?
The yield in winter is at best 4 food for a plot. That makes it hard enough to survive if you don't have reserves.
I'm inclined to disagree. You'd be working with narrower margins, sure, but realistically you would get by by planting and harvesting one field a day (so 2/6 workers). A smart person would keep a few fields extra and unharvested due to the narrow margins, but it would be about the same amount of effort as one would exert during summer or autumn to stay fed.
This assumes that you can defend 5, maybe 6 squares from attack (although the traditional 9 would be better for the extra fields), and without any henhouses whatsoever.
