Hi,

My FL2 has eco stop/start therefore has a AGM battery, does anyone know the average lifespan of one of these batteries? Are they better than a wet cell battery? Has anyone had a problem with these types of batteries?

Cheers all! Black MY2013 SD4 GS Auto, Wood Company Armrest, Freel2 sticker.
Gone MY2010 Freelander 2 Manual TD4.e S, Alaska White.

You can't put a figure on the life of any battery, agm or flooded type.
Some batteries can give many years of service, some just fail after a few years. it's the nature of the beast.
Just don't overcharge a agm, it's life will shorten.
Simple answer to your question is replace it when it fails. Another member of the failed FL2 clutch/DMF club, twice.