Apple Watch series 7 battery issues

I recently bought a series 7 watch and the battery wouldn’t last more than 2 1/2 hrs I sent it back to Apple and they sent me a new one. As impossible as this sounds the new one would not last more than 4 hrs with all settings picked carefully to save battery and not even using the watch only wearing it. I sent it back again and this time they are just sending it back with “couldn’t duplicate issue” status.

this means I’m still not gonna get more than 4 hrs of battery life from this watch and am just frustrated with this situation.

Any suggestions?