QUOTE(6UE5T @ Apr 23 2015, 01:23 AM)
In the olden days, batteries easily lasted 3.5-4yrs. My record was 4.5yrs using normal wet battery. But now even original batteries from my new car only lasted 3yrs while most batteries only last 2+yrs max.

Maybe battery technology development cannot catch up anymore with the car electronics development.
If you got batteries that can last 3-4yrs and have staying power even when the car is left idle for 2-3 weeks, then that's good.
Can consider deep cycle batteries.
Sharing:
I recently used a digital voltmeter, a battery conditioner and a 12V 1A adaptor to charge 2 batteries - first one is Kancil battery that dropped below 10V after leaving under sun for 2 weeks; and another motorcycle battery that went to 0V for a year.
The Kancil was left under the sun just overnight, and couldn't start the car the next day. I left it there for 2 weeks while waiting for the battery conditioner to arrive.

The motorcycle battery was used for over a year, then left in the car park. One of the cell dried up, and I filled it up with RO water.
Both batteries are wet type, and 2.5 years since purchase when they were charged.
Charged overnight and they both reach 13.3V and 12.8V, respectively.
The Kancil started up fine, and it's been few weeks since. It's a weekend pasar car, so it will be left there sitting a lot, and driven only for 3~5km each trip.