I think you'd see some benefit from biking 4 or 5 days a week, even if the rides are shorter.
If you want to be a bit more hard core, find any of a number of plans on "how to train for a century," and follow those for several weeks....even if you're *not* going to train for a century it will give you some idea of the kind of plan you get get on to increase your endurance and speed.
The Friel book is good, gets very detailed in places, but it's good.