I replaced one earlier this year on my 2007 WH CRD because the battery simply needed replacing. I hadn't had any issues with it in terms of leaking acid etc. The one replaced was a Century European style.
I replaced it with a MF88H Supercharge Maintenance Free Heavy Duty Battery.
Got it through Online Batteries Website
www.onlinebatteries.com.au. Cost $229 plus $22 delivery. It's better than the Century and has a higher CCA rating.