Don’t underestimate the value of your team’s (collective) experience.
When new folks come on board you can tell them how you do things and why you do things certain ways. You can share historical anecdotes about the reasons things are done these ways, but there is no way for those new hires to actually have the experiences that led to the decisions/policies/processes. They don’t get the opportunity to self-realize the lessons in the way that really drives them home.
There is also a huge amount of value in a breadth of knowledge about what the team has accomplished. At Crowd Favorite we have multiple small dev teams working on multiple projects at any given time. Lots of things are being learned, tested and built. We have “tech lunches” every two weeks (we had one today) to discuss these lessons with each other in an attempt to share that information as widely as possible.
I am reminded of this scene from Groundhog Day where Phil supposes, “Maybe [God]’s not omnipotent; he’s just been around so long he knows everything.”
The longer someone has been with your team, the more their value grows. Not just because of their capabilities and role in your company’s culture, but also because of their experiences and knowledge of the history of what you’ve done.