If the battery gets empty within 2 weeks, then throw it away and get brand new.
All my bikes have sitted in the garage for 3-4 month in winter time and the bikes start without any problems.
When changing battery, always make sure that you don't mix up "-" and "+" connectors. Always double check it before turning the ignition key.
10.7@205km/h - totally stock 04 ZX6R
10.4@218km/h - 06 ZX6R(stretched(LCR), geared(Vortex -1/+3), Full RS5, did 520 erv3, translogic QS, Ivans Servo Eliminator), Íhlins Steering damper - next target: 10.2