I'm sorry to hear you're having some trouble with your atrial fibrillation. If you have intermittent atrial fibrillation and your heart rate and blood pressure are normal, you don't need to rush to the ED. The '48 hours' people discuss is the window period that is often used to determine whether a patient can safely be "cardioverted" or knocked into a normal rhythm, either with drugs or with an electric shock. After 48 hours the risk of a significant clot forming in your heart starts to rapidly increase, so knocking someone back into a normal rhythm after 48 hours runs the risk of jolting that clot loose. That clot may then travel to places it shouldn't (like your brain, causing a major stroke). This is why patients with atrial fibrillation take aspirin or coumadin to prevent clots from forming when they are in atrial fibrillation. So keep in touch with your doctor, stay on your aspirin, and don't worry about heading to the ER every time you go into atrial fibrillation.
Best of luck.
I am in the middle of one of those "is it too long" I've been in afib since 5pm lastnight-about 24hrs. I've dealt with intermitent afib for yrs and my wife is urging me to go, however most of the time the symptoms subside after a couple of days. Always such a strange feeling that afib.