I replaced mine after 4 1/2 years - and it was a 1000CCA MF31-1000 from Battery Megastore. It finally died when I was away and the RR was left for 8 weeks without being started.
I replaced the battery with another of the same, and it was left at home, connected, for 6 weeks at the end of last year when I was away working in the US, and it started straight up when I got home, in the middle of winter.
So in short - it should last longer than 2 years, if there are no extra battery drain issues etc.
I bought the 3rd gen RF receiver to stop the interference problems (as in the past few years it's been left for a week or 2 at a time on a regular basis), and I also have LPG ECU which has a permanent feed from the battery, so probably draws a shade more than a normal one.
There's a good post on the Rangerovers.net forum which has been a 'sticky' there for years about battery charging etc, to help give and idea of the health of the charging system and cables. I've copied/pasted a summary below.. if you check those, and report back it will help diagnose if there is an issue with the charging system, power cables, or ground cables to/from the battery:
- Battery voltage, Engine off - before starting:
- Battery voltage, Engine started, idling, with no electrical load:
- Battery voltage, Engine running at 2000rpm with no electrical load:
- Battery voltage, Engine running at 2000rpm with electrical load (headlights/high beams, blowers on full, heated seats/screens on (where fitted)):
- Voltage drop from the alternator body to battery NEGATIVE post, Engine running at 2000rpm with electrical load. Use the DC millivolts range on your multimeter:
- Voltage drop from the alternator positive terminal to battery POSITIVE post, Engine running at 2000rpm with electrical load. Use the DC millivolts range on your multimeter: