How long can I SAFELY marinade boneless chicken breasts?!

I find that when a recipe says to marinade chicken for 30 minutes the flavor is just non existent.

So I'm wondering what is a good amount of time to marinade chicken breasts that's also SAFE. I want to lock in the most flavor.

Please note these are fresh not frozen breasts. And the packaging saying best before Monday October 5th 2020.

Vote below to see results!