My legs have been aching from the hips down the last few runs. I went out for a 10 miler yesterday and called it quits at 7. The legs just didn't have any juice left. So I decided that maybe my shoes had lost their bounce even though the mileage is only about 270. I let the clerk at my FNRS talk me into an upgrade to Asics Nimbus 10s and I'm thinking they'll work for me. I pay a little more for shoes at this store; I could probably get them cheaper at a big box store or online, but I like supporting local businesses, and I like that everyone that works there is a runner and I trust their advice. And this clerk just finished a marathon in these same shoes.
I just discovered a great reason to rotate shoes. I've never done that, I just wear them til my legs hurt then get a new pair. However, I read on a runners forum that if you rotate newer shoes with older shoes you can tell if the older shoes need to be retired because you can compare the feel to the newer ones. Genius! That's why I love running forums. You just never know what gems of wisdom you can pick up! I'll know tomorrow if the shoes were the problem; we'll see how my legs feel after 5 miles in the new shoes.