It leaves me wondering sometimes, 'Is this how I'm supposed to feel at the end of these?'
I wonder because I feel pretty much the same at the end of these runs whether they are 12 miles or 18 miles, and whether I run them very easy or at a moderate aerobic pace. Perhaps a good part of it is psychological. These are long runs afterall. Long enough for my patience with the run to wear thin. Long enough for my mind to start thinking, 'OK! Enough already!' Hell, they're long enough for my body to say the same, really.
In any case, far more often than not... I wake up the next day, and do the next run on the schedule, and I'm able to get it done, one way or another. I keep thinking that eventually some of the gains I'm supposed to be making by keeping up with the training schedule need to be consolidated, I need to allow my body to fully recover from all the tearing down that's being done, and realize the gains that I've earned.
Then, I look ahead at the schedule and see that there is, in fact, a "recovery" week on the schedule. It includes less mileage and is light on the harder work. Plus, I can choose to do all of the running that week as easy as I want, I guess. But, I wonder if that will be enough! I sure hope so.
With respect to making gains through training, I think I am seeing some. I've had several long runs that were run faster than I though I could do them, and I'm able to do them with less effort than I imagined it would take in most cases.
I guess that's a good thing.