The most important thing is to THINK the situation through.
The average human body digests one standard drink every hour and a half or so. It is entirely possible to eat a nice meal, have a couple of drinks with said meal, and leave the restaurant with very little alcohol still in your system.
Another factor which must be considered is the type of roads you will be driving on. If I am in an urban location where there are multiple lanes and lots of traffic, my personal limit is much lower than if I was driving home from a friends house and taking gravel roads that nobody is ever on. In all situations, I never drive "drunk".
Everyone is different, and those that drink more frequently are generally not as effected with regards to fine motor skills as those that drink infrequently, although their BAC is similar.
I think the whole "If alcohol touches your lips, you better not drive for the rest of the evening." message is directed for the lowest common denominator who may not evaluate their situation in it's entirety. Most people who practice self control in other areas of their life are able to tell if they are impaired enough that operating a vehicle could have bad results.
FWIW I also often have a beer or two while reloading, another taboo. It makes resizing and expanding hundreds of pistol cases on a single stage much less tedious. Dropping powder charges is always done sober.