What is the approximate battery discharge rate of Google Pixel 3XL phones when turned off?

I am considering purchasing a new Google Pixel 3XL Android phone, primarily for photography. I don't believe those phones have been manufactured for 2-3 years, so I am concerned about the battery health. If the phone has been sitting in a box for 2 years with 0% charge, my understanding is that it's likely the battery will not function well. For this reason, I'm wondering: What is the approximate battery discharge rate of Google Pixel 3XL Android phones when turned off? (Also, if anyone happens to know how approximately much battery charge was present when the phones were placed in their box, that will be helpful.)