Who knows what things will look like in 15 years. 15 years prior to now such a thing was not feasible, or would have cost 10x as much. I expect in 15 years the cost of home batteries will be much much lower, and replacement costs will be affordable. We're still in the very early stages of these products development and scale.
It's definitely going to be interesting to see, considering the replacement cycles of 15-20 for the batteries, and 20-30 for the solar array what the scaling, the costs, and what the net environmental impact is going to be.
Should be able to replace them easily - no idea how they are build, but one would expect a modular design.