I'm riding 2014 Dyna Street Bob. Everything is stock condition, nothing much added. My genuine Harley Davidson AGM battery is just over two years old.
I used a voltmeter to test the battery:
It is 12.5v when the bike is off
It is 12.2v when the light is on
It does not able to crank start

I used the CTEK MXS5.0 to charge it over night
I removed the charger and wait for one hour to test it again:
It is 13v when the bike is off
It is 12.6v when the light is on
It is 14.2v around 2000rpm

But it does not hold charge for ~12hrs and the cycle repeat again. I tried the "Recond" function from the CTEK MXS5.0 but it still don't hold charge more than ~12hrs

During these two years, there were two to three times I forgot to turn off the emergency light for about 20minutes and the battery not able to crank start. And there were two to three times I didn't ride the bike for two weeks, it didn't put on charger and it can't crank start. The past few months, the battery holding charge from around one week to three days to two days and this week around 12hrs. Is there anything else that I can test before replace the battery. It is a pity that the battery is just over two years. The bike had the alarm and ABS install from Harley Davidson when it is bought.

Can I say that the two to three times I forgot to turn off the emergency light for about 20minutes and the battery not able to crank start and the two to three times I didn't ride the bike for two weeks, it didn't put on charger and it can't crank start, is it the issue cause the battery to degraded and not able to use more than two years. And is it that it is better to charge one every few days if not riding for weeks because it is the alarm that draw the battery.

 

You already have 2 other threads on this. Not necessary.
I don't know if you can use Amazon, but here's a link to an excellent battery:
Just make sure it fits your bike.