Scoping is best, but I don’t always scope. Some examples why: Current horse had a mild colic where all diagnostics were normal. He’d been under stress and pain (we were trying to diagnose what that was about), and he’d also had a steroid injection, which in hindsight, he does seem to be sensitive to steroids. Due to the colic, vets thought that the stress of fasting and scoping would not be in his best interest, so idea was to try treatment for ulcers to see how he did. He didn’t colic again, but he also didn’t really improve. Because we had a big move coming up as well as a fire evacuation, I just kept him on Gastrogard for a couple of months. After the move, vet in new location thought his stomach was still NQR and suggested adding sucralfate 2x a day, with weaning off Gastrogard with a dose midday. After a few days, he became more relaxed and less spooky. We then started making more headway with his other issues. I still don’t know if he ever had ulcers, but he seems good now, a year later!
Previous horse I did scope initially. He had barely discernible grade 1 lesions in the stomach. Gastrogard was life changing for his behavior. He seemed to be seasonally sensitive in spring and fall and also sensitive around steroid injections. Based on his extreme sensitivity, we subsequently would just treat (or adjust preventatives when triggers were identified), because we did not expect a scope to reveal much. I suppose if he ever seemed to not respond to treatment in a predictable way, I would have scoped again.
I do know some horses with difficult ulcers that have taken months and different drugs to heal, requiring several scopes. Given that your horse has been through a lot, it would be reasonable to treat without scoping, same as why my vets and I didn’t want to stress my colicky horse with fasting and scoping.