My wife and I have talked a bit about this recently but haven't implemented anything yet. (I use 1Password, and she doesn't have access other than a shared vault, and vice-versa with iCloud passwords.)

One thing that gives me a bit of hesitation is from a security standpoint - if we have access to each other's accounts and one of us falls victim to, for instance, a password-manager-level phishing scheme, the fallout from both of us having to recover from that at the same time is dramatically more of an inconvenience than if only one of us is affected.

Happy to hear from anyone else who's thought about this and any approaches they may have been taken - there doesn't seem to be much discussion about it online.