I make a 12 minute steep with 15g/300g coffee:water ratio. A bit coarser grind than what I'd use for pour over. I (accidentally) found out I like it the most.
I like doing long steeps, but many mornings I say to myself "It's my coffee, and I want it now!" like on the payday loan commercial. Plus i always get a long steep on my second cup 5 hours later. It is basically espresso then.
I believe it is impossible to over extract with simple immersion…so it kinda doesn’t matter how long you let it sit, just that it be long enough (ie, the usual ~4 min)?
Hoffman’s tip about breaking up the crust and removing the “scum” — then letting it settle for a while longer — was the big game-change for me.