honestly you don't.... software updates are released and installed on vehicles that have a particular problem... BMW doesn't just offer it when it is available... (too many vehicles to update and the update process is very time consuming)
when they can't fix something they usually perform a firmware/software update (if a newer version is available)
if you don't have anything wrong with your vehicle you won't get an update... (unless you can justify it but coming up with a problem)
side note...
some of these updates offer enhanced features and functionality.. (like split screen on one recent update) resulting in some of us getting "creative" in convincing them to do an update!
check this forum from time to time for latest info....