I think you are very lucky to have such flexibility and it is a wonderful way to approach retirement and I like your math analogy
I am really ready to retire/quit (no retirement benefits) and try semi or full retirement, but recent announcements at work have made me postpone a bit. My company is undergoing major change, and many will be laid off in the next 12 months. The financial gain if I get laid off could be very good for me, so DH and I discussed staying another year now, and seeing if I get a package. If not I will definitely quit and relax!!!
My problem, a good one, is I am relocating to a warmer place very soon. So I am getting ready to submit a proposal to work remotely. I won't be asking for a reduction in hours, just virtual work. I have been telecommuting 2 days a week to prove that I can do it, but that doesn't mean my boss will agree to permanent full time virtual work.
It sounds like your approach is working so far, so do what works for you!!