Very good analysis. Obviously the market conditions will be constantly changing, which will impact the calculations.
I would think all Steem users should find a balance between holding and selling. We want Steem to grow, and if we hold onto our Steem and SBD, their value will increase. But in the other hand, each individual might need to cash some of their assets out. Just keep a balance so that Steem will continue to grow and not become a playground for scalpers.