[lomereiter]

You can shift your focus to mentoring your teammates and presenting at developer meetups / conferences. Simply tell your manager that you are greatly concerned about the bus factor (cite the 71% figure), and hopefully you two will figure out how to proceed.

[RangerScience]

Strongly recommend conferences. If you're feeling like you need some outside something to continue to progress your skills - which it sounds like you are - conferences are a great place to see talks that'll do that, and meet people who'll that. Even more so if you give a talk yourself!