I am still struggling with this.
I just realised that the spaced practice schedule has made me practise more massed practice! Usually I work with four pieces, but I have now expanded this to five pieces. But still, if I take breaks of two or three days, that means that many days I only have two pieces to work with during that day. Now, during a good practice day, I try to practise four times thirty minutes. That means one hour per piece, and that feels too long! And one hour per piece is actually massed practice.
My early intermediate pieces are not really suitable for breaking into parts either, plus most of the parts are too short to spend a lot of time with one part only.
A solution would of course be to work with many more pieces, but five pieces feels like the maximum of what I can handle.
So I am struggling...