"Andrew Mawson" wrote in message ...

Two reasons for premature bulb failu
snip

Is it premature, in this case? The OP wrote:

the bulbs in one of the fittings blows regularly (every 3-4
months), whereas the other fitting hasn't had a bulb blow
in years.

Both lights are left on most of the night.

Taking "left on most of the night" to be (say) 10 hours per day, an ordinary
1000-hour GLS lamp is only going to last 100 days on average - which is
3-and-a-bit months. 8 hrs/day would give just over 4 months. These figures
will be very sensitive to voltage, which (unless you're in an all-electric
storage heater heated area) tends to rise at night when the supply network
is lightly loaded.

I think the real question is "why has the other bulb lasted so long"? (And
the answer is probably just "luck".)

--
Andy