As you know Dave I am currently on a lifetime learning of a particular guitar piece. I have been at it 6 months and like you, when things seem unsurmountable (sp) suddenly another level becomes playable. As I don't work any more I can practice at any time of day and find that short (15-30 min) bursts reward me better than heavy long sessions. I also believe that learning in phrases or stages break down the piece to achievable parts.
Your statement that as you practice the next stage the previous stages become easier is a truism. I try and get to play a part so relaxed I could fall asleep.

As for jokes about accordians. I heard that perfect pitch is throwing an accordian into a burning skip and it landing on a melodeon is a perfect pitch. !