I was pondering the other day that as I get more experienced at running....I am actually getting slower :-) I have noticed the enjoyment of running and the desire to run for a long time has made me settle into a steady pace from which I don't really feel the need to get faster. It just lets me enjoy the running more and I figure that I will get faster as I get a lot of Kms on the legs rather than do what I normally do and try to force speed and then end up with an injury.
I have found this is especially the case with trail running. I am finding I go out with about a 5min - 5:30min average pace and it just lets me really enjoy the scenery in which I am running, which after all, is why you go running somewhere beautiful right. Otherwise you may as well run on a treadmill. I find when running at this pace and enjoying myself I get in great training sessions, saving any pace work I may have for the boring road, and manage to pass 20kms without batting an eyelid, no tunes required:-)