I have always used fairly short leaders/tippets, probably 10-12ft.  Today, because the fish were so flighty I experimented with a leader/tippet closer to 20ft.  It was much easier to cast then I imagined, resulted in no lost flies, I normally lose a few and only a couple of tangles with the vegetation behind... the last two might have just been luck, but I have gained confidence that it helped me trick a few extra wary trout.  For some reason I never really comprehended the advice to use long leaders on spooky fish until today....