It's possible you could ride 60 miles now without the hand problems. I've found that problems I had during my first century resolved themselves simply by riding more. You (and your hands) are in better condition now. An increase in average speed of less than 1mph may also be due to the fact that your conditioning has improved.

Whether your increased speed is due to improved fitness, placebo effect or a faster bike, or quite possibly all three, you're riding longer and faster and enjoying it more.

Not for everybody, but I wouldn't mind having one.