I use 10s, sometimes 15 or 20s... but on stage I have used 30'ers. For microphones I have used 50 and 100 footers for live speech (I did audio for a wedding). There have been tests to show how many feet it takes for you to notice sound quality drop off, I think around 20 was noticeable but not that bad. Also, how many connections you have is important, running through a pedal board with 2 connections per pedal and 10 pedals will create noise and lose tone. Thats why its good to get a line selector so you can bypass a large pedalboard when its not in use.