It's a simple procedure. If you buy a fresh liquid from a good vendor, it might need a little time just for all the ingredients to mingle & as they do, the liquid changes, mellows or sometimes get's more pungent.
Some vendors will sell you a liquid ready to vape straight off or they might have info on the site telling you how long it needs.
An example then, I have here some vanilla custard dated 14th march. I havn't started it yet because those kinds of flavours taste better from about two weeks on in general & then get better again. It's in a dark cupboard & i go to each day, give it a shake up & squeeze out the air a few times, lid back on & another shake. I might remove the lid & leave it overnight a here & there so it can breath. Basically i work with it until it's ready.
I was sent an RY4 liquid & that one tasted fine as soon as i got it. It was also a fresh liquid. Maybe it will be better after a steep too but i can vape it in the meantime.
Some fruit flavours are known for being ready straight off the cuff.
If you are buying imported liquids, big name stuff then i cant speak for those. What liquid are you using if you don't mind me asking ?