For IAH, there is a 2 litter of alcohol per person limit. I had to pay duties on wine only once. I got stopped because of a bag of poppy seeds my boss asked me to bring back for his wife. It was the kind used in the bakeries not the illegal kind. Unfortunately, the agent did not want to take any chances. Once I got stopped for the poppy seeds, they decided to go through the trouble of taxing the extra bottles of wine. It was not a lot of money but it took a bit of time. After that experience, if I am traveling with more than 2 litters of wine, I am careful about the other stuff I carry.

Basically, if you are traveling with more than 2 litters per person and have to go through Customs at IAH, don’t make it worthwhile for them to tax you.