CF (my bigger one) is also 17.
He is currently on hi-fi lite, high fibre cubes & a drizzle of D&H 16+, as well as glucosamine once a day, and of course his favourite garlic & parsely in Linseed oil drizzled over the top
His feeds are very small tho at present - more a token (particularly breakfast as he really only gets a bucket then so I CAN catch the little horror ), tho will be increased again come the colder weather or when the work required is harder.
What I feed suits CF's figure, needs & current working regime of 6 days a week, all mixed hacking/schooling & RC activities, all an hour or more.
As Ester said! My 28 yo doesn't get veteran feed, she has Suppleaze Gold and Gut Balancer, fed with Spillers Cool Fibre. If it ain't broke, don't fix it. My mare is a picture of health!