I think this is one of the best mods to do for your truck, so I installed the LMC Headlight Harness very early on my truck. A little bit over a year the lights would start to flicker on after washing the truck - which I generally spray down the engine bay. It got to the point it was more than a flicker and I started to have problems days, if not a week or more after washing the truck
It seems the relays that LMC Headlight Harness uses aren't that sealed from getting moisture/water inside them. It was fairly easy to pop off the top cover and I saw moisture/water inside. LMC sent me replacement relays and I easily popped them open too but then used epoxy glue to hopefully seal them good from moisture/water getting inside. So far so good. I even bought a extra set and sealed them too, just in case.
Other than that, I love this upgrade for the headlights and dealing with the relays wasn't all that hard.