I have a 16 year old Tennessee Walker gelding that I have had for 11 years. In that 11 years I have put A LOT of miles trail riding on him. He still has the heart to go and go fast. He loves to be out on the trails and is like the energizer bunny. Last time I took him riding we went out for about 2 hours and on the way back he was all go and was trying his hardest to run back to the trailer. I did notice however that we he would go up hill he seemed to be having a really hard time, almost straining and was slipping a lot. Do you think this could be to age or something else? When do you think a good time to "retire" a horse from trail riding is? We do a lot of riding and for hours at a time, I just don't want to push him to hard and have him hurting himself. Just looking for honest opinions. Thanks!