As someone who's been expanding slowly overall, I send my excess dwellers who I have no training slots or jobs for, out to explore. It works great to ensure I'm stocked full of weapons and outfits all the time and gives me a lot of caps as well as gives my surplus of stimpaks and radaways a purpose.
However... due to how poorly optimized the game is overall, just tapping the wasteland to check my explorers takes 1-2 minutes to populate info on the first explorer then about 5-10 seconds for each explorer after, nevermind the insanely poor frame rate while doing so. When it's all said and done and I've checked stimpaks and radaways on everyone, my resources can go from being at 95% happiness and totally maxed out, to red simply because I've been unable to collect resources for so long just trying to check explorers.
I understand that 50 dwellers is a lot and I don't intend to have this many as I expand to accomodate them, but really.... the optimization is atrocious. This is a mobile game, being run on a wide variety of devices and while my iPad 4 isn't brand new, it has more power than most mobile devices and still runs crappy.
I love this game so far, it has a lot of potential and bugs seem to be rather seldom overall, but really, the optimization issues are really frustrating.