Actually I've already mitigated this by disabling automatic MMS download, and from what I read [1] it can be mitigated in other ways as well. It can't be done in every app, but then you can just use an app that lets you do this. So this is a non-issue. Any others you can think of?
The app-level "mitigation" is that media isn't automatically loaded. You are still just as vulnerable after you decide to play that innocuous-looking MP4 file.
I wasn't aware, thanks for mentioning that. However, the videos I watch are on YouTube and news sites and such... not sketchy sites. And I never play MP4s on my phone directly (unless they're videos I've recorded). I'm not sure many others do either, frankly. So how much do I need to worry and how much of a justification is this to upgrade the phone every 1-2 years?
Right this is sort of the point. You were not aware, if you had based your defense against unlatched vulnerabilities based on your knowledge 24 hours ago, you could quite easily have gotten pwned. Knowing about all vulnerabilities that could affect you and how they work is incredibly difficult. I don't want that risk (nevermind that even if I was ok with that risk, my company would throw a fit if they found out I was using an unpatched OS).
[1] https://en.wikipedia.org/wiki/Stagefright_(bug)#Mitigation