how about you get that battery checked out?
after you do, get a battery tender aka battery manager (amazon has them for like $20) and use that whenever your car will be parked for a long time. i use it on both my G and Z when they will not be driven for more than 2 days. my commute is too short to charge the G's battery full each time.
also check you water level. it's easy to maintain these batteries. just need a flash light, funnel, and small bottle of distilled water.
my G's battery is 8yrs old which is the original. absolutely no issue.