The problem comes when you notice that a chord seems a bit off, so you find the B course is out, and tune the offending string back to pitch, then discover that, though the pair now match pitch, they are off from the E pitch above, but in tune to the G course below, so you retune E the course above, and when you've got it right, you strum a chord, only to find that
the e's are of from the octave of the low E string--so you check and make sure that the D G B are in tune, then check the Gs on the high E string, and decide that it is the octave of the low E that is out, so you retune it and match the lowest E string, then you play a G chord and discover that the B notes on the A course are out of tune with the open B course, and when you fix that, you notice that the high G string in the G course is a tad off, and when you tighten it, it breaks and when you put the spare on, it breaks, as well, and now you are playing an 11-string that is still out of tune. About this time, you decide the tune would reall sound better on your six string;-)