Description of usage from the howToUse class message in Delay:
"An instance of Delay responds to the message 'wait' by suspending the caller's process for a certain amount of time. The duration of the pause is specified when the Delay is created with the message forMilliseconds: or forSeconds:. A Delay can be used again when the current wait has finished. For example, a clock process might repeatedly wait on a one-second Delay.
The maximum delay is (SmallInteger maxVal // 2) milliseconds, or about six days. A delay in progress when an image snapshot is saved is resumed when the snapshot is re-started. Delays work across millisecond clock roll-overs."
Boris Gaertner March 04, 2005 Delay class >> shutdown is used by SystemDictionary>>processShutDownList:
The shutdown list itself is a class variable in SystemDictionary. Inspect the class variables ShutDownList and StartUpList to see that class Delay is registered in both lists. Alexander Lazareviæ Classes that register themselves with addToShutdownList: in SystemDictionary get the message shutdown: sent to them on image shutdown. See SystemDictionary>>processShutDownList: