Mine used to last about two weeks in winter with a thatcham alarm (oem batts). They would charge up ok though, but if the bike isn't used in winter, the loss of batt power was very noticeable. When the batt was on it's last legs, I got fed up and used to disconnect it when I wasn't riding the bike. The alarm is the culprit though. On my old bandit, which didn't have an alarm, it still started after 6-8 weeks of not being used. If you have a power source, as the guys said, an optimate will keep you happy.