Fifty milliamperes is maybe a bit high for a modern car with a lot of "energy vampires" roosting in it, but not by much, and is small compared to a healthy, fully charged car battery. Two questions come to mind.
How old is the battery? If it's original equipment or maybe even an older replacement in a 1997 car, you've definitely gotten your money's worth and in fact should be commended for the care you take of your car -- most people are probably lucky to get half that.
Also, though the details you mention make me guess that you're the sort of person who wouldn't knowingly suffer loose or dirty connections on either the hot or the ground side, one must ask: are you seeing 14.4V actually across the battery posts? Not at the car's side of the battery terminals -- actually on the battery's side?
As others have mentioned, a good sanity check is to disconnect the battery for a day or two, if you can be without your car for that long, and see if it's being drained or just has gotten too furry inside and/or too low on electrolyte to hold much of a charge.
Cheers,
--Joe