My first game uses 62 megs on iOS and I've seen it crash on people, who are using a lot of apps at the same time. Hell, it even crashed when the Touch Arcade editor played it in their stream last January using a brand new iPad. I was horrified! Gladly it worked the second time he tried, tho.
There's really not much you can do, except designing small games that run well on mobile and testing the game you are building all the time with the lowest device you plan on supporting.
In my experience everything above 100 megs could experience frequent crashes.