Depends...For me if I'm in a studio and the song/beat is mixed right it usually takes about 20 minutes (if you know how to use their mixing board whether it be a SSL, Icon, etc.)...My advice is never mix and/or master songs consecutively. You always wanna mix or master with fresh ears (Virgin Ears). The purpose of mixing and mastering is to have the song/beat sound alike in all stereos without clipping, distortion (remember digital cuts at 0db and analog cuts at 6db), hissing, etc. You wanna use Studio Monitors with good wattage to mix/master your songs
