Same here, plenty of areas with a bus factor of one. Even worse, one of the critical persons is over 70 - incredibly sharp, healthy and keeps up to date, I hope to reach her age with those skills, but her age makes a health problem more likely.

That said, her irreplaceability is more due to stupid security setup (she's the only one that has all the necessary privileges), so I guess she could be replaced eventually after some hiccups (and at a big hit to productivity).