I believe there is a point of diminishing returns
Back when my bankroll grew to over 6 figures I saw that the number of games where I could play with the larger max bets and some type of longevity would be fewer and fewer, and decided not to increase my bankroll further. Of course, I am not a full time player and am not looking to support myself on blackjack earnings.
There does come a point where if one had a million dollar bankroll that they could not get enough hours, or get too many backoffs, to earn a six figure income from that bankroll. Perhaps banking team play, with all the pitfalls of having team members, would be the best method.
ihate17