I think until the IPO shares are sold out, all mined BTC should be paid out as dividends (after subtracting expenses). IPO shares are currently being sold to raise capital for rigs, and paying the maximum dividend will help sell those shares more quickly.
After all the IPO shares are sold out, maybe 50% of mined BTC could go to purchasing new rigs (growth) and 50% could be paid out as dividends?
That's an interesting take. Paying out all BTC generated until the IPO was sold out would still allow for growth, as half of the dividends paid out (my half) will be reinvested into the company to pay off my shares.