My BR is $2,500. I four table on .25/.50 .
It's not just about bankroll, it's also about winrate. I can win apprx. $30/hr fairly consistently in this system.
When I play higher stakes, I have to play more thoughtfully. I can't four table 1/2. I'll play two tables. And I generally have to be more selective about what hands I play, what position I play, who I get involved with etc. The swings become larger and I'm not convinced the profit is higher hourly.
So it's not just about bankroll. It's about level of understanding the game.
I will play $30 hyper turbos, and occasionally open a couple tables of .5/1.00 Zone poker to mix things up. Or I'll play three .25/.50 and one .5/1.00.