It's been said that the three nastiest environments for electronics are in aerospace, undersea and automotive applications. For us, automotive applications are the most common, of course, and you have to contend with engine and exhaust heat, weather temperature extremes, automotive chemicals (water, oil, gasoline, tranny fluid, battery acid, power steering fluid, windshield washer fluid, rear end lubricants, brake fluid, etc.), extreme vibration and G-forces and road chemicals such as deicing salt and oceanside salt-laden air.
Any time I make wiring connections in an auto, I use uninsulated crimp connectors, crimp the connections and then solder the connections and cover them with heat shrinkable tubing, usually two layers. Automotive crimp connectors suck as they are mashed-together crimps and not the gas-tight crimps of the electronics industry. So the solder insures a good connection and a heck of a lot of mechanical stability against vibration and shock (mechanical).
If you look at the factory wiring for most autos at the lights, there's usually nothing more than a rubber boot around things. They rarely go to the trouble to encapsulate or conformal coat things. On the other hand, they're figuring a life expectancy of just a few years for the entire auto, so they don't worry about lights that last 100 years.
Dean