I have just done my headlight loom upgrade.
First off: do you have an MQ or an MK? This will make a difference.
MQ's have no relays in the headlight loom, MK's have one relay, but it does not switch power to and from the light, it simply separates the left and right headlights. All power still runs through the switch. This is a very bad setup!
Putting higher wattage globes in puts extra strain on the wiring and the weakest link will break. In both MQ and MK this weak link is the switch. Over time they develop a high resistance and will eventually start to burn, my switch did this and I was only running 55/60w globes. With my upgraded loom I have no more burning switch issues and the light is much better even with low wattage globes.
A headlight upgrade is fairly simple still and I can provide a wiring diagram and am happy to assist with questions. If you are in Vic I am even happy to help you wire it up.