My senior also started to become prone to colic when he was 29-30 years old. The first one was out of nowhere, I had this horse since he was 3 and he’d only ever had one or two colic episodes before. It was relatively mild, resolved with banamine, and we chalked it up to a fluke. 6 months later, he had a similar episode, slightly more severe. And finally, 6 weeks after that he had another episode, the worst of the 3 but still resolving with banamine and time.
My horse was on regular Equioxx for his arthritis and so we suspected potential ulcers or lipomas based on signs/symptoms. Unfortunately he really needed the Equioxx to be comfortable and I was terrified of losing him to a strangulating lipoma, so after the 3rd colic I made the difficult decision to let him go peacefully. SL are a terrible, painful way to go, and I didn’t want that for either of us to be his last memory. While I miss him terribly, I know in my heart it was the right decision.
Something you may want to consider if he colics again. I truly hope your story ends differently, it sounds like your boy is lucky to have you and has a great setup. Sometimes there is only so much you can do when they reach this age, despite wishing differently.