Thanks Oded! I have little experience to draw from, but what I know is that the benefit from mentorship fluctuates over time. The 6 months range (12 meetings, more precisely) is just a guess right now. I'm not setting it up as an expectation with my clients, but I do emphasize the flexibility by saying 'we'll meet as long as it is helpful'.
I have no concern with constant acquisition of new clients. I actually benefit a lot from these meetings, even those that don't yield a client engagement. This is my view into the ecosystem, and it helps me hone my offering.
If I get to 80% gross margin on my time (1 unpaid hour for every 4 paid hours), I'd be very happy. Optimizing for more efficiency may be counter-productive. For example, I don't want to prefer clients based on their 'risk of graduation'. Quite the opposite - I want clients that are forced to scale fast, and may 'make or break' while at it. Risk is good!