Well, I'm not suggesting you or anyone else just run out and ride one (I'm a stickler for training - not to say you aren't in amazing shape!). But with that said, I never rode over 120 before my first double. Some people train on shorter, harder rides than mileage (i.e. they don't do much over 75 on training rides but they make them tough with climbing, etc.). Each person is different. But no, I'm not joking. You already have a base. If you WANTED to do a double, you could train (using a method that suits you) for four to six weeks and knock one out without much ado, woman. I honestly believe that.