Apple smart battery case

Hello to the community.

I recently bought an original smart battery case and I'm confused😕 about the operation.

It seems using the case first and when it's empty it starts using the Iphone battery.

This is the functionality as it was designed. But wouldn't it damage the case battery over time since it stays for 2- 3 days at 0%?

All the Iphone battery care tips say not to leave a Lithium battery discharged for longer time.

So in low power mode I can survive with the phone only battery 3 days. During this time, if I not recharge, the case stays totally empty.

Does it shorten the live time of the smart case battery?

I would like more the discharge mode where both batteries used simultaneously or at least the option to choose between modes