How do I keep drawer knobs from loosening over time?
I'd recommend going with a metal knob that's held in place by a machine screw. They're going to cost more, but they won't get damaged from everyday use, and you don't have to worry about them stripping out. Most of the knobs in my house are metal and take machine screws. I do have to periodically re-tighten them though. Some Blue Loctite might take care of it, but I've never taken the time to address the issue.