Cardiac arrhythmias tend to progress, or to evolve into something less manageable. I use the term 'intractable', meaning the same thing, not easily controlled or dealt with. Because they tend to progress, especially atrial fibrillation (AF), it is always best to deal with it firmly and early. You either are willing to take anti-arrhythmic...AND....rate control medication when in AF in order to keep the rate at or below 100 BPM ideally, or you take a mechanical remediation (NOT a CURE!!, just a control measure that is done electrically, not by medication), which is catheter ablation. There are several ways to perform the ablative procedure, and they're improving on them all the time.

If you control the progression of fibrosis (which is a changing structure inside the atrium endothelial lining and below that into the muscle itself), which begets 'remodeling' of the substrate of the myocardium, you can take drugs for a very long time...in some cases. Many patients find, though, that they eventually need an upped dosage of the same drug, or that they quickly lose ground and must be placed on another drug, often a more potent drug like amiodarone (which you should only take when all else fails and you still want to live for as long as possible. You can do your own googling of 'amiodarone' and read up on it for yourself. In case you become dismayed, I was on it for ten weeks two years ago out of necessity. I'm still here..., and so are scores of others who have been on it for years. Every patient is an individual case, and that includes tolerance to flecainide, Tikosyn, Multaq, Sotalol, propafenone, and the various beta and calcium channel blockers.

So, that's a long way of addressing your question, and it can be summed up like this: many, most, cases of cardiac arrythmia, but especially when unmanaged, will tend to get worse over time. This can come about even with pretty solid control using drugs. Happened to me, and it has happened to thousands of others. I finally realized that only an ablation was going to rid me of the accursed AF and its awful symptoms. Unfortunately, even ablations can lose ground to the heart which is always looking to effect the electrical disorder somewhere else from where the ablation lesions were made during the last ablation. IOW, even ablations might need to be touched up in time, maybe six months, maybe six years. Some never have to have another ablation. I'm just past two years free of arrhythmia, but it took two ablations to rid me of it.

I have said a lot. I can get windy, sorry, but if you need further information, please do consider doing a google search with 'atrial fibrillation and management' or something like that. Or, 'anti-arrhythmic drugs and side effects', or even 'duration of efficacy of various anti-arrhythmic drugs'.

All I know is that a former cardiologist told me that it might not be effective down the road, so I might need to change to a different medication if and when that happens. That was nearly 20 years ago, and I'm still on flecainide .