I have a FLHRSE3, 6 1/2 yrs. old, same battery that came from factory, has not give any indication of getting weak but they say the life of these batteries is about 7 yrs., Just wonder if i should go ahead and replace it, would hate to be caught out in the middle of nowhere and battery lay down on me. 
Anything over four years is a bonus, and I've personally gotten between five and six years on my bikes in the past. Unfortunately, when the battery decides to "lay down" it will tend to do so with very little if any warning. Bike (or car for that matter) starts and runs fine today, tomorrow morning it doesn't even turn over.
You could go to the trouble of doing a load test on the battery to get an idea of the state of the battery, but even if a battery passes a load test it can still fail due to internal short circuits or opens due to failure of the internal cell connectors. If it were me, I'd consider myself lucky to have gotten one to last over six years and put that puppy out to pasture.
btw, I've noticed in recent years that the batteries don't seem to be lasting as long as they once did. I'm not sure if its due to cost cutting in the manufacture of mainstream batteries, or just the added electrical load late model bikes and cars have compared to their predecessors.
Jerry