When the wall switch turns off a bulb, the bulb will normally show up in the individual bulb list as in "off" state in less than 10 seconds and as "offline" after at least 20 minutes. It takes time for the server to tell apart the "offline" from a temporary transient "off" state that can be caused by specific wall switch operations such as bulb resetting.
Note: While the bulbs are in "off" state, they will show up in the home screen as still being "online" and as active in the device list until they move into the "offline" state.
Bulbs will not be able to report "off" state to the server in the following scenarios:
Even though the bulb will not be able to report "off" state in the above three scenarios and the server cannot detect them being "off" right away, the server will eventually be able to determine that the bulbs are indeed not online if it failed to receive any messages from the bulbs after 20 minutes and declare they to be "offline".