Per https://github.com/mozilla/sccache/blob/a310f6a62eb34281bda083f88dc96c736a3eeb74/src/server.rs#L69-L76 this variable controls how long
the server waits before shutting down. For long compiles that exceed this timeout, this can cause compilation to fail like
servo/servo#19495. https://github.com/mozilla/sccache/blob/629813f2d2f0b3ac8102696df69d57200688d320/docs/Jenkins.md#L11
describes the effect of making this timeout zero for CI infrastructure - the server process becomes long-lived and never shuts down.