Dead battery after two weeks...normal?

[Ricochetron]

I recently purchased a 2007 boxster. It had a dead battery when purchased so the dealer gave me a new interstate battery. I fully charged it, installed it and the car was not driven for two weeks. I go out to get in the car and find out the battery is dead, reading 4.1 volts on the battery terminals. Are these cars battery hogs?

I have decided to get away from wet acid batteries and order an Optima for the car. To avoid ruining the new battery would you recommend that I install a battery cut-off switch or trickle it after every drive, which will be once a week or so.

I have never owned anything which pulls the battery down this quick!