I agree with the others -- it doesn't look like you are over-training or getting old. It's natural to feel tired at night after a hard ride. If you aren't tired, you probably didn't work very hard. I commute 30 miles/day about 4 days a week with a long ride on the weekends. When I overdo it, I have trouble sleeping at night and have trouble climbing and maintaining a fast pace when riding. However, I'm "tired" in the evenings just about every day. I consider that one of the benefits of regular exercise because I have no trouble sleeping.