I just learned the phrase "circus factor" ("If you or someone on your team ran away to join the circus, how stressful would it be for the rest of the team?") and I like it much better than the widely-used phrase "bus factor". https://mercedesbernard.com/speaking/minimize-circus-factor/
@josh I do think it's important to specifically organize teams so that it's okay for team members to go on vacation. For example, one of my explicit reasons for setting up PR auto-assignment for Wasmtime was so that I could go on vacation. But the difference is that normally one is expected to come back from a vacation 
@josh I agree, that would certainly be a nice change compared to common practice!
@josh I hadn't read all the slides in the talk I linked yet and it turns out PTO is a major point there too:
When folks take PTO, actually let’s back up. Do people take PTO? Do they feel comfortable taking PTO? When they take PTO how much planning and prep needs to take place beforehand? How many meetings get scheduled on the calendar to take advantage of their time and knowledge sharing before they leave?