With that heavy of a workload, I don’t think you can go wrong with a joint supplement. Probably a moderate one with that length of riding, 6 days a week. Supportive care is always beneficial in my book. I began my 7 yr old shire cross on a daily joint supplement and adequan injections. We work hard and I want to give his joints the support they need to stay strong. I highly recommend using a supplement with high levels of hyaluronic acid. Do some research on what levels of ingredients are most beneficial, Smartpak has the most wide selection of supplements.
Just my opinion though! Joint supplements can be so overwhelming!