Steeping is the process of aging your e-liquid. It is certainly not necessary for all e-liquids, but some vapers swear by it, and whether a flavor should be steeped is a matter of individual taste.
There are a few different methods to it, but the purpose is usually to get rid of the “perfumey” flavor/taste some e-liquids (especially citrus) have when they are freshly manufactured, or to allow the flavorings in the liquid to intensify. Some vapers recommend letting your e-liquid sit with the cap off to achieve this, but we do not recommend this. E-juice is very easy to contaminate. If the wrong bit of dust gets into your e-juice, it could ruin the flavor for the entire bottle.
Our recommended method is to just let it age naturally with the cap on, and make sure you shake it well before use. If you want to speed up the process a bit, you can let the e-juice “breathe” by opening the cap and exchanging the air between the cap and the e-liquid every few days.
Steeping will also allow any water in the VG (one of the ingredients in your e-juice) to evaporate, thus strengthening the flavor.
The best thing to do is taste your e-liquid as soon as you receive it, then if you find it tastes/smells “perfumey”, or you just don’t enjoy the flavor, steep it for 1-2 weeks and give it another try.