Hiya,
Like Feneris I am doing the Bristol course and studying between 3-6 per day. I have commented before that once I've done four hours my head is in burst bubble mode
and if I do do more than four hours it is to review stuff I hadn't quite got. Magnetism and dip leap to mind:o
I too find I'm getting between 80% - 90% working like this.
Hope this helps...