Best way too keep battery in order to ensure lifetime

Hi there, I'm new to PS4, I bought one just to play FIFA Ultimate Team without cheaters. Being a FUT "addict" made me run away from FIFA on PC. There is an option to disable Bluetooth and use USB only. I know this option wasn't there on the original PS4. I have my PS4 connected to the same monitor as my gaming PC so I don't really need it to be wireless, I don't mind the cable since I'm sitting close to the screen, and maybe I get less input lag, who knows. So my question is, what is better for the battery? Keep it almost empty, middle charge or fully charged? I think it didn't come charged when I unboxed it.

Thanks.