he does look in good condition for his age, but I would say his weight is such that he has no spare reserves of fat to help keep him warm when the temperature drops, and as he gets older this may cause a problem, so I would monitor him carefully. Also his coat does seem a little thin and raised in the picture, which can hide the actual weight under the hair. If he were mine I would probably like to see a little bit more weight on him if I am honest. All of mine have lived until well into thier mid to late 30's, and I admit they all get rugs of medium wieght, for the colder monthes of the year. If you feel the base of his ears, it is a good indication of whether they feel cold or not. I also go by facial expression, my older mare gets a very pinched look in her face when she is cold, which as she gets older, is becoming sooner, in each year. Like barry g. I like to rug, because I think they appreciate the comfort of warmth , the same as we do, but, I also think it helps to conserve thier bodies energy, helping them to live longer, with less health problems. As we get older our bodies use up more energy just to function, and in cold wet windy weather, it needs to burn more, just to keep warm; therefore if you provide the extra warmth, the energy can be used for keeping the body healthy, rather than wasted on keeping warm- if that makes sense. This applies to horses as well as humans.