I think the mobile market has a short attention span. Because of the limited interface mobile has, most games are probably played for a very short total time on average (there will be exceptions of course).
Things that I have read is that it's a pure numbers game, which would make sense given the statement above. Your best bet to survive (if you aren't the lucky big hit game) is to turn out a new game every month or so. You track performance and ignore the bad selling ones and put your attention towards the ones that are selling, while still putting out new games and marketing.
I think this goes against what a lot of game developers want to do, which would be to put time and energy into a game they really believe in, vs turning out a lot of smaller games. Different market, different strategies.