I had all kinds of trouble with LED license plate lights overheating to the point that the LEDs would desolder from the board underneath them. I suspect this, *not* the condensation issue, is why packing tape works to keep them alive longer (as the license plate bulb areas are most certainly very aggressively sealed and I've never seen a drop of condensation in mine). Molton/hot solder has an incredible amount of surface tension and I bet packing tape gives that little bit of extra stick that keeps all of the connections sound for a while.

I'm sure the voltage regulator ideas linked would solve that problem (a quality regulator won't get hot like garbage Chinese LED assemblies, and it'll be somewhere it can be equipped with adequate cooling), but that's a lot of hassle. What I've done instead is just encased the cheapest "can-bus" (aka w/ load resistor) LED bulbs I could find on eBay in clear epoxy - that way none of the joints desolder. They're white PCB, had no heat sink, and had 2 LED modules with 3 emitters each, and are plenty bright for license plate lights.

I'm sure I'm reducing the life of my LEDs by many orders of magnitude by running them incredibly hot, but even if they go from the ~20,000 hour lifespan of a typical LED to ~400 hours, I'm fine - that's a few years of headlights-on time for me.

For what it's worth the bulb holders are very hot to the touch after operation but I've been using this LED setup for probably 50 hours of headlights-on time (about 9 months of driving for me) and nothing's melted and my LEDs aren't noticeably dimmer than when I started. If you're the running-lights/headlights on all day style, your results my vary.