Guys do the right thing. If your app is very sensitive to bad data (say financial) just throw up a temporary "down for quick maintenance" page for a couple of seconds and you are good to go.
Downtime affects SLAs and there isn't a lot of breathing room depending on your 9's[1]. In addition, bringing something down has its own problems and are you just advocating bringing down the user interface or should everything get shut down, like the entire stack? All the services, queues, databases, block storage, etc?
