We have two sconce lights on our wall. Each has a single light bulb
(the candleabra) style. I put the bulbs in a few years ago and have
never had an issue (the bulbs were within the wattage range for the
fixtures. The last two times the lights have been on for a few hours
the bulbs begin to emit a burning smell and small pufts of smoke is
coming off the bulbs. The fixture itself is still cool to the touch
(as is the part mounted the the wall). The bulbs have a filmy/sticky
feel to them now...

My assumption is my wife must have sprayed something near them and
whatever it is coated the bulbs and is burning off.... Sound
reasonable? She can't recall though. Any other reason two fixtures
that have worked flawlessly for several years (with the original bulbs
still in them) would suddenly have this issue? I have a TV on the
same circuit and its fine...