Mercedes, he has been treated for ulcers for years before I got him and I don't have a lot of history on his husbandry, just vet records to go off of. However, I suspect that it had a lot to do with being stalled and a lesson horse as he is a nutter butter OTTB and hates a stall and inconsistancy (eg. a new student rider every time he is taken out). When I got him he had been moved three times in three months so I think that contributed to the problem.
I like the idea of natural treatments very much but with as much damage as recurrent ulcers for years and years have caused I am skeptical at how much they can help. I say this because I have ulcers too, which bleed from time to time, and the only thing that really helps get them under control is omeprazole and watching my diet and stress levels very carefully. Probably not a bad idea to add some of these things to his diet to see how he does though!
Most of the ulcer products out there are largely herbal based when you get right down to it.
Herbs require 'time' to work. They are slower to show results than conventional medicine. So for an ulcer attack you'd want to go with something that relieves symptoms immediately. For maintenance you can then go with slower acting things like the herbs.
As with anything, it's going to require some experimenting with types and dosages until the best combination is achieved. You might even experiment with the form of herb, whether it be dried, cut and sifted, a tea or a tincture. The different forms bring forth different properties and strengths of properties.
Obviously, your biggest challenges will be keeping a good balance of gut flora, and preventing a rise in PH level. So, having him be able to munch 'all day long' on hay would help, as well as daily supplementing of a probiotic. That may be enough on it's own, especially if you are managing his stress levels with turnout and exercise.
In the end, you know him best so go with what feels right for him.