Currently I gig with 4 guitars, one tuned to standard, one to drop D, one is a 7 string, with the B alternating between regular B and drop A, and one guitar tuned to what I call Black Sabbath tuning, all strings tuned down 1,5 step to C#. I might add a 5th guitar tuned regularly, except for the low E dropped down all the way to B. But I have to draw the line as 4 is already stretching it and the 7 string can cover that low B sound.