You would have individual logs for each COMPUTER so that if a new user logged on, it would update/overwrite the log with the current users details.

You could use a script then to read all of the logs and look for a specific user name and then have it tell you which log file it resides in.

I have a code example if you really want to pursue this method.

The DC query method is not very practible for organizations that have DC located around the World. On AD it is not as much of an issue as the user should be pointed to a local controller instead of a random list of 3 like NT 4 does.