^^^ Same observations and findings as your stated as we go through the mentoring process. I have a few years left in my day job before I plan to retire and have this fill up part of my days.
Key reliable, well paid person is key to the operation. I have that implemented in my laundromat so same type of effort here only that it is a bit more intense when something breaks down primarily do to the fact that I / we are learning the process.
I'm very much ok with having to work a little more as the ends justifies the means. I am not the just sit in rocking chair person and wait on my time to be up. Not yet anyway. I don't like to fish and I am done traveling. To date out of my close to 35 years and counting, I've spent 12 of those years traveling.
Personally, I think that this is a reasonable substitute for a next step for me post career.