..... i know a guy who preaches that the diesels bust bulbs quick due to the vibration......its plausible.
I can't agree with that one. Unless you drive your truck in the Baja 1000, light bulb life expectancy will be more affected by voltage level than anything else. Excessive current flow is the mortal enemy of light bulbs. In a nut shell, with a constant amount of work/load, current flow will be higher with lower voltage. Current flow will be lower with higher voltage. (Ohms law)
It has been shown the there can sometimes be a voltage drop of 2 to 3 volts or more at the headlamp connector compared to measurement at the battery, AKA: voltage drop. This is due in large to headlamp current having to pass through small gauge wire for a excessive distance. Current must travel from the source through the harness to the headlamp switch in the cab and back through the harness to the headlamp at the front of the vehicle.
I have installed one of the readily available aftermarket headlamp harnesses and found it makes a visably, noticeable differnence. They use heavier gauge wire and re-route the current so it travels a shorter distance. It now only has to go from the battery direct to the headlamp via a relay, which is what allows you to turn it on & off.
I used to go through a headlight bulb about once a year. About 3 years ago, I put in a headlight harness and Silverstar bulbs. I can honestly say the difference is like night & day (pun intended), the improvement is very noticeable. Since I installed the new combo, I have replaced 1 headlight bulb in the last 3 years where it would have been about 3 bulbs at the rate the bulbs used to fail.
Pure Diesel Power handles the headlight harness and is a site sponsor.