My understanding is that if you can provide 12VDC the bulbs will last
longer. One interesting thesis that I am not sure about but has some
element of truth was that to low a voltage is also bad because halogen
bulbs rely on getting hot enough so that some weird chemistry occurs
that allows the filament to be re-built from the boiled off metal. This
apparently is the trick to halogen bulbs and why they can get much
hotter than standard bulbs hence be more efficient.

BTW have you come across IRC halogen bulbs. They are very efficient (a
20W IRC halogen is the same light output as a standard 35W halogen). I
have just put some in and the place is like a stadium its so bright.

Steve

Glenn Ashmore wrote:

I have heard that 12V halogen bulbs do not last long running at absorption
charge voltages. A couple of smart regulators (Ample Power being one) have
a halogen lighting feature that limits alternator output voltages. I picked
up a couple of 40 amp DC/DC converters on eBay and was planning to use one
to power the electronics. Would it be worth while to use the other for the
lighting circuits? Especially the nav lights which are harder to change
out.