put it on a charger and charge it at least 2 amps even go to 6 amps or so for about 8 hrs. A battery maintainer charger will not charge a dead or depleted battery it will only maintain the charge on a good charged battery. A battery should be charged to get an accurate test to determine if it is Good/Bad As far as how long they last will depend on the battery brand. My OEM Yuasa lasted over 7 yrs before I changed it and it was still starting the bike just fine. I have seen members buy cheaper online batteries that only lasted a year and others that lasted 5 years. also to check the voltage with the bike running you should rev
the bike to about 2500 rpm
to see what the voltage is and it should be charging in the mid 14's volt range. After you have it fully charged if it drops to 8.5 volts when cranking the bike over the battery is junk.