NiFe batteries are great for longevity, and can be completely discharged without damage, but they are very inefficient cf Lithium batteries, and their operating voltage range is much higher than other battery chemistries, so inverter selection becomes a bit trickier. NiFe batteries are only generally used in backup systems in difficult/expensive to get to places, and have not generally been used in a daily cycling situation such as in a house. How they might perform in such a situation is a big unknown at this stage IMO.
I’ve lived off-grid since 1991, and have used a 21kWh LiFePO4 battery since late 2012, and used Lead-acid before then.
Batteries have always been the main expense for off-grid installations, but I’m still waiting for often repeated “cost of batteries is coming down” to happen. Lithium batteries are significantly more expensive now than when I purchased mine in 2012, mostly, but not solely due to the $AU exchange rate changes.
Lithium only makes up a small part of Lithium batteries- I think there is more Copper in them than Lithium, and significant amounts of Aluminium too, and all these metals can be recycled, but I’m not sure if anyone in Australia is actually recycling Lithium batteries at this stage. However, I’m sure someone will be doing it in the not too distant future.
I’ll be hanging onto any dead cells I have until they can be recycled, they certainly wont be going into Landfill.
As far as batteries being an economic proposition for grid-connected houses, financially it just doesn’t add up at the moment - payback time is generally longer than the warranted lifetime of the battery. However, if you value other considerations, such as having electricity during a blackout (only a limited range of inverters can do that), then the value of grid connected batteries increases significantly.