As Monster said, some juices are good right out of the mailbox--usually they also improve with time. I know there are people who vape Mt. Baker right out of the mailbox. So, try it, and if you aren't liking the taste, then let it sit. I almost always try my juices the day they come if they are new flavors because I am not all that patient! Once you get a few extra bottles, you will find it easier to let the new ones sit for a bit.
I got some juice from Bionic Vapor on Friday and started vaping it yesterday...it was just fine. Might get better, good to go as is. So, give the juice a try and then decide if you need to wait.