Warm bath to thin the VG and help the Flavor "Spread". ( I use the bowl of hot tap water and it sits in there til its cool method.)
Shake the piss outta it, multiple times doesnt hurt.
And have at !
If ya wanna see what the difference is a week later, make a big enough sample so as to have some to save back.
My experience has been.....
It ALL tastes better after at least 24/48 hrs.
Some are good right after mixing, but 24hrs later they "Settle", or "Meld" a bit and get a little smoother.
But you will get a pretty good idea of what its gonna be like after a GOOD mixing....... later it just gets better !
Now the exceptions...............
Most Tobacco flavors benifit GREATLY from steeping.... some you will not recognize 3 weeks later as that same funk you tried right after mixing, but that will be few and far between as even Tobaccos will give you a hint of where they going right after a good mixing.
( Steeping will not magically transform a horrible recipe into Something Great.)
Creams, chocolates and coffees almost ALWAYS do better with some time under their belt... how much depends on your taste. ( And will power to save it !)
Again rare......
But I have had some flavors fade as time passes.
Blueberry, Key Lime, a few other I cant recall ATM.
Now this does not mean they get wasted..... Key Lime softens a bit losing its "edge', and gets sweeter.
So I gauge for that when using it.
Tops off in my experience has only been necessary for Flavor concentrates that contain alcohol.
Theory is to let the alcohol flash off and evaporate..... Does it work for sure ?
Maybe the steeping alone would have done it..... but slower....
All just my Experience.........
Have fun and figure it out...... thats the best part !