Hi Ken, well it sounds like the propranolol is doing the job if your symptoms have disappeared. That's good news. Like any medication its up to you and your doc as to how long and how much you need them and betablockers aren't the type of meds where you have to increase the dose because your system gets used to them, once the right dose for you is found you can usually stick to it for however long you need them.
Over the few years ive been taking them, they have given my system enough of a rest from constant anxiety with an irregular heart rate, to actually be able to reduce them these days without the worst of the old symptoms returning. I'd rather be on these than on tranquilisers or similar.