Well done Stolly. Do you have a minumum time/distance rule?

Im currently trying to run twice on 2 days of the week tues/thurs and 5 days overall. I got a book on how to run quicker (by Julian Goater) and he says mixing sessions is what its all about even if some are just 20mins very steady in am and then intervals/quicker for an hour at night. Hope it might speed me up a bit (and I'm too fat!).