The change of message is very clever. And IS working.
It is clear from behaviour that we DO NEED a constant message reminder.
Even if it only saves one life it is worth it.
At what point would you stop telling a child about looking right and left when they cross the road etc?
However, we DO NEED TO CHANGE THE MESSAGE periodically because we can become IMMUNE to messages, just as we do to most things after a while.
And here we are (along with millions) discussing and arguing it - which makes us aware, or 'alert', once more.
Which we were no longer doing for the previous message.
STAYING ALERT is an obvious and good 2nd message.
As the child grows learns how to cross the road safely - they do not need to spell out - nor shout out - about looking right and left - But they do need to STAY ALERT to what they now KNOW are the dangers.
We are being asked to STAY ALERT to the fact that there are bullets flying around in the air that can kill any of us.
Watching out for the bullets - and the people carrying invisible guns who are unaware that the gun is firing - means STAYING ALERT.