1. Headlight bulb life is as heavily dependent on the vehicle as it is on the wattage. Some vehicles have a reputation for short lived bulbs, probably mainly due to how good the cooling is, which varies enormously between designs, but also the level of vibration it is subjected to. (also see 2.)
2. Headlight bulb life (and brightness) is heavily dependent on the voltage the bulb gets. After decades of good bulb life on the 110, I started blowing headlight bulbs - turned out to be the alternator had decided to run excess voltage. This also probably explained the melted stoplight lenses, which I had blamed on poor grade of plastic in replacement lenses (due to fading).
If you are finding headlights inadequate, the first step is to check the voltage at the lights. If it is below about 13.8v with the alternator charging, you need to find out why, and fix it Increasing wattage will only make it worse. Landrovers before Defender did not have headlight relays, and headlight wiring is barely adequate for the standard wattage, and woefully inadequate for anything higher. And there are often poor connections, especially earths, to make it worse. I fitted headlight relays to both my 110 and 2a, giving a marked improvement in light, on the 110 supplying the relay with power from the alternator battery terminal, and on the 2a running an extra earth wire from battery to the radiator support as well as supplying power direct from the battery positive - which has a direct wire to the alternator. In both cases the lights were dramatically improved.
3. An intermittent connection to the headlights, either power or earth will rapidly blow bulbs. SImilarly, continuous operation, with lights switching on and off every time you park, will shorten bulb life.
4. There seems to be some difference in life between brands, but it is minor compared to the above.
John
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol
From memory the 60/55 W was the legal limit, or close to it.
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Originally Posted by TonyC
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