Almost exactly one year ago, we switched Zombies, Run! - a fitness game - from being a paid app ($4-8) to a free-to-play app with subscriptions ($4/month, $20/year). Unsurprisingly, I'm delighted by this announcement, because it rewards apps like ours that provide long-term value and entertainment for our users.<p>Clearly a subscription model isn't for many apps - probably most apps. But it was right for us, as we've been maintaining and improving Zombies, Run! for over four years now, and every week we add new content. With a subscription model, we only get paid if people decide we're good enough to commit to over a long period of time. Since we're about helping people exercise, I think that's fair enough.