Is it really necessary to spend hours upon hours tweaking and adjusting the rear derailleur to get it just right, or are those who claim to have mastered this art simply more patient than the rest of us? Can a well-adjusted rear derailleur truly make a significant difference in performance, or is it all just a matter of placebo effect? Furthermore, how do we define mastering the art of fine-tuning a rear derailleur - is it purely about achieving a silky-smooth gear shift, or are there other factors at play? And finally, are there any hard and fast rules for adjusting the rear derailleur, or is it all just a matter of trial and error?