If you don't use your car all the time, it would be beneficial to invest in a battery conditioner.
I have mine plugged into an Optimate.
I have a waterproof plug permanently connected so i just plug it in when i park up.
Get both: a new battery and trickle battery charger/conditioner, something similar to CTEK.I have an 05 and I think my battery is the original based on all the service records I have. The last service it had the dealer report said the battery was marginal. Now that it's cold I see the car cranks slower than normal. I run it every other day just to charge the battery. I'm not sure if I should get a conditioner or a new battery maybe both. Based on the fact that it lasted 11 years I to am thinking to get a battery from the dealer.