No medications convert me so I always have to be electrocardioverted( have had 10 and two ablations). Due to the fact I'm not on any anticoagulants I have to be converted within 48 hours. If you wait seven days you would have to be on an anticoagulant and in therapeutic rangeto be electrocardioverted. I haven't heard about a time frame to determine if you are persistent or paroxysmal. A good site is this one: http://www.stopafib.org/what.cfm
Steve
I can't answer your specific question but I will offer the view that if the AFib episodes are recurrent without periods of months of remission between you should discuss corrective strategies with your doctor. It may be simply taking more Flecainide, or another drug.
As far as electrocardioversion is concerned, it is my opinion (I have had 4 electrocardioversions with some success, but always returned to permanent in my case) that it would not increase you period length of normal sinus rhythm over what you get converting on medication. I say this based on my experience that when I went to electric shock to convert, I was thereafter dependent on medications to keep me there. This lasted up to about 18 months a couple of times.