I think i always took one day for OChem and Gchem to go over every section...and at the end i went over only the questions which i made mistake on my first or second attempt.
But for bio it took me complete 2 days to go over every questions at first. But the second attempt took only one day. And anything that was new to me but appeared on destroyer, i kept writing in a notebook, so at the end instead of going over every questions, i went through my notebook. In that notebook i wrote everything that was given in the explanation or anything useful from Wiki or from Campbell.
But definitely Destroyer is easier and less time taking if you are using textbooks rather than review materials.