As one who has been playing for many years I fell into a rut.Then from subscribing to this web-site I began playing open chords,major,and minor scales,and most importantly,to keep the same tempo,and to play all chords and scales clean.No slurring notes.I breezed by the first chapter,and am half way through Chapter 2.Its not about speed though.As long as one can proficiently play a piece of music,then move on.Thats the rut I fell into.Playing the same thing over and over.I Try something new from the lessons.Hope that helps.On my days off from work,I can play all day.After all,music should move you,IMO.Some stuff is tedious,but I just plug through it.How long should one practice?I practice as frequently as I can.This web-site has re-taught me some important guitar lessons,and enriched my love for why I play guitar.