When is enough enough?

My recent upswing is getting me closer to enabling me to enter the next level up: .1/.25 games. I'm no stranger to those games; prior to my multi-tabling effort (starting June 13th), those games were where I spent most of my time. However, now I typically run at least 3 tables of .05/.1, and currently have a bankroll of ~$175, which could support 1 table of .1/.25. My question, though, is what is proper bankroll management for multi-tabling? Is it simply the number of tables you plan to run * the 10 buy ins, meaning 30x buy ins for me? That means I need to have about $600, which, obviously, I have a long way to go (I typically buy in ~80% max buy in). $600 seems a bit too steep, though $200 seems a bit too shallow. I will probably hang out at the .05/.1 level for another month or two before I make a move. I think the option I will likely go with will include a combination of .05/.1 tables + a .1/.25 table. For the time being, I am going to watch the .25 tables for soft spots.

Is there any bankroll management guidance out there for multi-tabling?