If you are having problems with rough environments, maybe you should just try and "pot the whole board"( minus the connectors you will use)... paint it with epoxy resin. That should seal it and still allow for heat transfer, if that is any kind of issue.
Actually on the note of this, I've done this twice so far, and as long as I make sure that there is a little piece of aluminum stuck to the voltage regulator and a couple other things (probably doesn't help them) with some heat sync compound stuff. And the piece of aluminum comes up out of the resin, the thing becomes nearly un-damageable. ( I heatsync the the VR even though I probably don't need to cause the airsoft batteries I run can be up to over 9V so it can heat up a bit)
I've been using this method on all the arduino stuff I make for airsoft because radioshack project boxes are broken through by the airsoft BBs all the time. I potted up one of my arduinos a bit inside of the project box, the thing can take shots from a real BB gun, and I haven't damaged it in any falls or tossing it in my car either.
With regards to overall longevity. Well I've got an arduino uno thats about a year or so old, thats been assaulted by about 500 different sketches (it was my tutorial unit) and different pin usages. Definitely drawn too much current from several pins on several occasions. Thing still works fine. And its been built into a temperature sensing jig and running constantly for the last 3 months with the exception of shutting it off to put a new SD card in and reset the timer.
Theres another one in use on a machine by a friend of mine thats been in constant operation since 2009 with the exception of power outages and its still fine.