Even if you know the app store flow is fragile, I doubt anyone can tell whether it'll turn in 6-months or 6-years.<p>If you are an expert in making money there, ride that wave -- looking for something comparably-lucrative-but-different is a distraction. Optimize the hell out of your current flows -- find ways that spending $1 in marketing makes you &#62;$1, create small variants, port to other platforms, outsource -- with careful metrics so you detect early when your strategies are played out.<p>Meanwhile, on the side, sock some away in a completely safe non-distracting portfolio. <i>When</i> it makes sense to turn your attention elsewhere -- either out of the app store opportunity ending, or a desire for something new -- <i>then</i> that safe cache of money will help. But at this point, you've already got a lucrative place to spend your attention -- why dilute it with other plans?