I see you've never had an issue that needed someone to immediately and reliably answer. Even I've had to rely on PagerDuty's ability to both persist in calling

I see you've never had an issue that needed someone to immediately and reliably answer. Even I've had to rely on PagerDuty's ability to both persist in calling and fallback to the next person (all with a history to audit) when a super serious issue occurs. The key though, is for PagerDuty to only be invoked very rarely, so that it isn't becoming abusive.