Sally I am surprised that your dr hasn't given you any medication for reflux before now. Most premmies do have reflux and need treatment for it.

Is he is pain, is he loosing weight or disinterested in eating? These are signs that he needs medication.

I was told a long time ago that all babies outgrow it by one, and a large number do but not all, my son is almost 3 and a half and still has reflux.

You can ask to see a specialist gastro dr to discuss testing or a general paed to watch it all. There are medications to stop the acid content but none really to stop the vomitting, since this is due to a muscle problem that meds won't fix, generally time fixes it. So it all comes down to how is he doing generally, if he is gaining and eating well, but just vomitting a little, then i would leave him as he is, but if he is in pain or irritable, not sleeping, not gaining etc... then I would definately ask for some medication.