So my group really likes the winter rolls... but not the amount of time it takes, so I’ve tried to streamline it a bit, making a document that is able to simulate some of the rolls that my players are really interested in the result of but doesn’t want to roll.
It rolls for horse survival and family member survival.
The chance of dying has been changed because all the numbers I have seen have way too high a mortality.

Age 1-3: 5% chance of dying each year
Age 4-11: 1,7% chance of dying each year
Age 12-34: 1% chance of dying each year
Age 35-49: 5% chance of dying each year
Age above 50: 10% chance of dying each year

Chances of dying are doubled if you have been besieged at some point through the year.

How does these numbers sound?

I have attached the document if anybody is interested.

That gives about a 60% chance of living to 35, which doesn't seem completely unreasonable. Chance of reaching 50 is 28%, which isn't absurd either.

I certainly agree that most of the official and semi-official mortality rates are ridiculously high.

You ought to check the revised Book of the Estate, where the mortality rate has been fixed.

Or you could just take a look at this thread:
http://nocturnal-media.com/forum/index.php?topic=2420.msg18545#msg18545