I can't figure out for the life of me how to quote "I particularly don't believe in routine..." all neat-like. But something I picked up from "The Principles of Correct Practice for Guitar" is to live for 'now'. Get "lost in time" because as soon as there is a sense of time everything goes wrong ( I've seen it ) and it blinds you from your PLAYING. If you can't see through everything else to what you are doing wrong, you can't hope to ever fix it, and thus you will be making "horizontal" growth all your years in playing. So this is a pretty serious issue, don't allow yourself to be trapped by time, when you are playing, time does not exist (nor does anything else). In the past few weeks I've been playing about 7-8 hours a day ( I am part of a group called "The unimployed" )
but I could get it whenever and in any increment at a time. It has really helped, I feel I've made months of progress in days time. Check out "guitar principles" and sign up for the free newsletter email. One last thing and then someone else gets to talk, a metranome is the only exception, but I only find myself using a metranome for about 1-2 hours of those 7-8, to help me learn particular songs and increase speed in scales.