Here you go.. for what it's worth.. I don't bother with it tho, personally.
A study conducted by the US Department of Agriculture’s Nutrient Data Laboratory calculated the percentage of alcohol remaining in a dish based on various cooking methods. The results are as follows:
Preparation Method/Percent of Alcohol Retained
alcohol added to boiling liquid & removed from heat 85%
alcohol flamed 75%
no heat, stored overnight 70%
baked, 25 minutes, alcohol not stirred into mixture 45%
baked/simmered, alcohol stirred into mixture: 15 minutes 40%
30 minutes
35%
1 hour
25%
1.5 hours
20%
2 hours
10%