For me 5.5 to 6 sot is normal, and that's with all the various tweaks, and since I got the phone. That said if I had experienced 8hrs sot I would also try to figure out how to go back to it!
My phone still lasts a couple of days between charges since the Android ¹³ update.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help.