Well , I am 52 and started playing when I was 40...I only get to play an average of about 4 hours a week...I break the songs down into parts just as you do then put them all together very slowly to start with then increase speed till I have it...unfortunately my musicality does not come naturally..my rythym and speed suck at my age :) so it takes me about 2 to 3 weeks to nail a song like Barracuda for eg.

Shane