Yeah, that's my feeling as well. I'm not a Principal but I've seen people promoted to the position burn out.
I'm content being in a senior engineering role where I still get to do technical stuff (and yes, some mentorship as well). Then again, I don't define my life by my career, I'm OK with doing interesting stuff and earning a decent paycheck without climbing up the ladder. Alas! Eventually I will age out of this possibility. I'm already dreading it.
