I've got a 2005 FLSTN that I purchased just a few months ago. The bike had spent most of it's first three years in a garage, wasn't rode much; I'm putting about 1K miles per month on it now. It's pretty much stock, no electrical add-ons of any sort, and I haven't had any starting problems with the bike.

My question is: what's the reasonably expectable battery life for this bike?

 

3 to 5 yrs depends on cold cranking amps. It's best to float charge your battery, also if it isn't a sealed battery check to cell if you have any dead cells before you do charge. Also it is best to charge a battery and then add water to the battery.

 

I got 5years out of mine, put it on a tender every winter it might of gone longer but I did not trust it after 5 years

 

Unlike some of the other bikes, a softail battery is surrounded by a hot container of oil. This will reduce the life of any battery. 3 to 5 years, like 2099d says, is a good estimate. Being an '05 your bike probably still has the factory installed battery which is a sealed unit. Keep it charged and the connections clean and tight and it will last a long time.

 

The battery tender will greatly prolong any battery's life I use one year round because the charging system does not accomplish a full charge at all times, being about 14.5 on the meter if one sits any at all it will discharge some.

 

OK, sounds like something I need to acquire... H-D has the "SuperSmart® Battery Tender®" that turns itself on and off as needed, so the battery never overcharges. Stock # 94654-98A, $39.95.

Is there a better option that someone can recommend?

 

If you are putting 1,000 miles a month on your bike and don't store it for the winter, I don't see why you would need a battery tender.
IMHO, the main reason they sell battery tender's are for garage queens and winter storage.
I have had 7 bikes and never have used a battery tender. They don't usually put battery tenders on cars, unless they are going to sit for quite a while.
What happens when your battery is close to the end of it's life cycle? The tender may keep the charge up just enough to get you started, but what happens when you stop some place else and it doesn't start. You can usually tell when your stater is turning the engine over a little slower. I would much rather have to replace a dead battery while the bike was still in the garage.
Tom