Oak, my body falls apart from an immune system kind of thing. It happens after every tour/hard effort I do, not always in the same way, though. It depends on what else is going on, how rested I am, etc. It just so happened that DH got sick a few days after my last metric, I caught the germs, and I probably was in a little bit of a depleted state. If I come back from a tour and it's nearer to the end of the summer, it often just shows up in a decrease in my average speed. Funny though, that didn't happen when I went to Spain, when the trip was the last week in May. I did do a lot of training very early in the season, for that, and a lot of nordic skiing that winter, too. I didn't have any physical problems, i.e. back or hips, or anything during the last metric, either during or after, so all my PT paid off.
I want to do the century because I want to do another century. I just want to finish, and I probably will be the slowest , as from what I see more of the "racer" types sign up for the longer distances at these kinds of lower key events. I don't feel that I "should" do it because it's local, but more that I always feel more relaxed when I know where I am, the nature of the roads and the climbs. I like knowing what to expect. I had a serious anxiety attack on a very steep climb on the last metric; it was on a road I usually do in the other direction... that way is hard, but this was worse. Despite this, I passed some of the racer boys on that one. That has never happened to me. Usually I get "angry" at the hill and it motivates me!
I cannot sign up for the metric and decide to do the century, as they start 2 hours apart. I can sign up for the century and decide to do less there, though, because I'll always be in a place where I will know how to get back in a shorter distance.