Im new to brewing but i went 10 min past what the recipe called for on my first batch, so did 30 min then sparged the grains after they drained just to get the remaining sugars out. Hope that helps, ya dont really wanna do more than 30 min cause then it starts to release the tannins in the grains, or a ceratin temp. Did mine at 155 degrees, and dont go past 170 degrees.