Sigma.40, I would check your charging system: it should read Above 13.6 Volts @ 2,000+ RPM, across the battery terminals (use a digital voltmeter). I would also recommend a voltmeter/battery monitor on your bike, permanently. It is the best way to monitor your charging system and battery, ongoing, so your bike won't leave you sitting.
My understanding is that flooded batteries should read 12.6 Volts, two hours after being disconnected from a charger (called "resting voltage), and an AGM should read 12.8 Volts, resting, if they are good. They should also register at least 11 Volts, when cranking, if good.
If your charging system is working, are you idling your bike for more than five minutes, on a semi-regular basis? Idling means the alternator is not pumping enough voltage to charge the battery -- it is discharging while the engine is running. This can kill a good battery by letting it run down too often. Also check your electrical load: are you running too many Watts for your alternator to charge your battery? Did you follow the maker's instructions, to the letter, to initialize your new batteries? If not, their life will be shortened -- it varies by maker, and model. Several possible reasons your AGM's are not lasting. Cheers!
