Every one should be able to take leave and not kill your project at any time. If that's not where you are now the project is at risk. Someone might change jobs

Every one should be able to take leave and not kill your project at any time. If that's not where you are now the project is at risk. Someone might change jobs just as much as mat/pat leave. You should make sure that no one person knows how do perform any task that is needed. Even/especially soft skills like being "leader for a day". Or being "last word on xxx" for a day. Or driving some change. If you do that without fail the team is able to cover anyone else. Any team of 7 people has one 7th the extra workload when someone is absent, but nothing should stop working. When you are 7 again, if its the person with knowledge back, you are up to speed immediately; if it's someone new, it takes time to get back to where you were. If you work like: this when it's your turn to be off, noone will miss you, or curse your absence, and they will be very pleased when you are back. In short "spread the work across the team" and "temporary promotions" as everyday practices, before and after expected leave. This approach pays off immediately, shorter absences such as plane delays, crisis at school or someone just being late to a meeting, are easier to deal with too.