Determines how long slaves can remain idle before being stopped or terminated (see the Stop/Disconnect on Idle Timeout setting).

Times are expressed in minutes, and a value of 0 (or an empty string) indicates that idle slaves should never be stopped/terminated. Positive values are simple time-outs after that many idle minutes. Negative values cause the node to time out when idle and within the specified number of minutes from the end of an hourly EC2 billing period.

E.g. if a node has an idle timeout of 5 and at 11:30 it has been idle since 11:20 (10 minutes), it will be terminated. If it has an idle timeout of -5 it won't be terminated because the hourly billing period doesn't run out until 12:00.

If a node has an idle timeout of -5, and it becomes idle at 11:58, it will be terminated because it's within 5 minutes of the end of the billing period - even if it was active less than 5 minutes ago.