We are a specialized firm so literally nobody else can do what we do and we have to get called in when there is a problem. That said, in other orgs I ran or was in prior to this current one we had “on-call” and “escalation” schedules that guaranteed time off to anyone not on the schedule. If you needed to be brought in off schedule you would be compensated a bonus at 3x hourly (calculated as yearly salary ÷ 640) and be removed from your next schedule rotation. If this was a recurring issue with a particular employee’s skill set, redundancy was added to that position. It wasn’t a perfect system but at least there was an effort made.