Since the update is coming OTA, Verizon implores you to have a good Wi-Fi or cellular signal and says to budget 3 to 5 minutes of your life for the update to download. Installation onto your device should take another 3-5 minutes. While it installs, you won't be able to use your phone, even to make an emergency call.
At the end of the few minutes it takes to install the update, you should feel better knowing that your Motorola DROID RAZR HD or Motorola DROID RAZR MAXX HD is now once again secure.
source: Verizon (1), (2) via AndroidCentral