Idle termination time for the agents of this label, in minutes, counted from the moment the agent came online rather than from the moment EC2 launched the instance.

The value means the same as the Idle termination time of an AMI: 0 never stops an idle agent, a positive value is a plain timeout, and a negative value times the agent out within that many minutes of the end of an hourly EC2 billing period.

This wins over the Idle termination time of the templates the rule matches unless Let a template override the idle termination time is ticked.

It is also the rate at which the spare target fades: once per idle termination time the target gives up one Hot spare step, towards the work the label still has in sight while it is in use, or to Hot spares once nothing is asking for the label at all. When idle termination is off, the default of 15 minutes is used for the fade, otherwise a target raised once would never come back down.

An agent is only reclaimed once the target has faded past it, so a spare the label is still counting on outlives this timeout. Reclaiming it would pay for the same capacity twice, because the next pass would immediately provision a replacement, and a build would wait for that boot.