I examined the line voltage with an oscilloscope, hoping to find it
loaded with spikes or have an oddball shape (triangle-like or clipped).
Looked perfect, both from black to white and black to green.
Next time I'll check the circuit breaker box for loose connections.

Even though the voltage measures about 120, I'll get her 130V long-life
bulbs. I turns out that the bulbs that go the soonest are the ones that
are switched on most often.

In the kitchen fan, which is rarely used, I pulled up the center contact
in the one socket (out of three) whose bulb blows most often. When I
replaced the bulb, I did it with the power on and tightened the bulb
just about 1/4 turn past the point it lit, as someone suggested, to
prevent overtightening. I can't see an easy way to replace just the
socket, and replacing the whole fan assembly is too expensive and not
worth the effort.

Thanks, everyone, for the interesting comments and suggestions.

R1