Regardless of the discipline that you ride in, regular maintenance is likely a common theme around your stable. This is a great video featuring the USET Veterinarian Dr Richard Wheeler. He talks about the different types of injections for horses, how often you should do them, if and why you should do them and what the benefits and downsides there is to each.
With that said I still think it is wise to listen to your vet about what they think is best for your horse in the end.
This video was filmed at the Robert Dover Horsemastership Program in Wellington Florida in 2016.