Noting that before Long Life fluids were introduced, BMW appear to have recommended changing the fluid every couple of years, your car which is filled with Long Life fluid - is unlikely to need a change for some time.
Obviously, if you believe the "Lifetime Fill" message, it will end up being a self-fulfilling prophecy, but you still shouldn't need to touch it for several years.
But, it's your car, so change it when you feel like doing so.
HTH