If I only have three days a week to train I would do a long ride, an easy ride, then an intense ride in that order. Do the hard effort stuff on the day before your rest day. If I can do somewhere around 70 miles one or two days a week leading up to an event I can go 100 for the event with proper nutrition. And I'll say this whether you care or not, eat when you're riding. Even a 30 or 40 mile ride is much more productive if you have the energy to train all the way to the end. Showing up to the last 10 miles and barely being able to turn your legs won't help anything. Also, sometimes in the week or two before a race I actually put on a little bit of weight. I figure it's better to be a little heavy with strong muscles and lots of energy than to be light with a weakened endurance.