I've adapted a suggestion from "The Musicians's way". I don't have the book here so I hope I'm not misrepresenting him but this is what I do now ...40% of practice time is spent on learning a new piece to the point you can play it competently but not upto tempo or with your full interpretation in place.20% developing a piece or pieces you've got past stage 1.20% on maintaining repertoire, playing through pieces you've learnt previously so you don't lose them.20% on technical work. He also recommends you take notes and make plans for each practice session so you have specific goals for each piece. I'mm bad, I don't do that. I really should.And I go through those steps, usually, in that order. In fact because I'm anal/OCD I use a timer to divide my practice, otherwise I just play all the pieces I already know and avoid working on the new one.
Thank you for this, this sounds very helpful indeed. A lesson to all of us I'm sure.