I don't have specific numbers, but in other batteries of this type, the length of storage time before discharge affects the efficiency. Heat stored from compression is lost over time.

I was curious about that as well. I think it's best application would be to compensate for large amounts of rising and falling generation from solar grids, that way the cycle is daily. Being quick to come online and meet demand makes it good for maintaining grid stability at a much lower cost as well, like the Hornsdale Power Reserve facility https://hornsdalepowerreserve.com.au/.