So I made an interesting discovery tonight while working on the kitchen cabinets. Most of the doors do not stay shut when they are closed. The "snap" to lock them in place is gone. So, I took the two hinges off each door, cleaned them, oiled them, and then noticed that the flap that attaches to the door is not perpendicular to the hinge as it is supposed to be. Some were worse than others. A vise and a hammer solved the problem, so the wrap around brackets are now square.
Here are the hinges. (Taiwanese crap)
formatting link
When I put the doors back together, the doors now remain shut. They're not as tight as I would like, but I imagine the 22 year old hinges might want to be replaced. If I can find one that is identical, that's what I'll do.
I just thought I would pass along this information for anyone else who is as clueless as I am.