Stretch it...
Is it good or to stretch? If you ask me, which you probably do if you read this, then the answer is that you should absolutely stretch if you want to maintain or improve your mobility. There is no conclusive evidence that the exercise response gets better if you stretch, but mobility definitely becomes better if you challenge all joints, muscles and ligaments.
As a rider it can be difficult to find the time to stretch, but you don't necessarily have to do it every day! Start with stretching after your workouts, i.e. those who are not riding. If you "just" ride, do it when you get home, watch a movie or talk on the phone; that is, at all times when you can and it does not interfere with what you do. Whilst chatting to people at the stable; throw a leg up on a chair or stool and stretch a little! You do not have to do the whole body at once, take it a little now and then to begin with, you might find you start a new habit ;)