I might be out of shape, but about 13 miles into my commute, I feel like I'm about ready to be done. Of course then I get out of the shower at the office and back to my desk, and I'm ready to not be at my desk anymore and be back on my bike.
Last week the weirdest thing happened. I'm tooling along for the afternoon commute on the MUP, a little slower than I was in the fall, not quite representing the awesomeness of my Tarmac, and some OLD guy (I'm 40) comes blowing by me on a cruiser with 3 packs over the rear wheel. I wasn't expecting to be passed I guess because he startled me! I call out to him, "on my left!" And then I felt a little embarrassment at being passed by such a rider. On the other hand he did execute a solid pass, maybe he had just started his commute and he was fresh, so when I caught up to him at the intersection, I stayed behind him. A moment after the light changed was when I realized, he stormed off much faster than his effort and weight would permit, he was electric assist. And at that point it was on. I couldn't let him get out of sight as long as we were on the same route. He didn't.
Moral of the story, if you're going to blitz by people on the MUP, get a fricken bell or say something.