With age comes maturity. It's allowed me to get along better with my co-workers (so many upper 20s, lower 30s tend to be a bit... hot headed) and I'm not afraid to negotiate. The older I've gotten, the more comfortable in my skin and in my skill set I've become.
If there's ageism I've yet to experience it and I've worked with people well in their 50s doing mobile. It comes down to who you're working for, what your skill set is, timing and, in my opinion, health. You've got to stay healthy and look healthy! Also, I tend to prune my resume, no one wants to see your experience 8+ years ago.
Or maybe it's all luck, ask me in five years what I think when Objc/Swift goes the way of PHP, I might be singing a different tune.