Shaking is always important, not just when the juice is first mixed. Different flavorings have different densities. Also, nicotine itself has a higher density than PG or VG. Both flavorings and nicotine will settle to the bottom of the bottle in time. Always shake before use to keep it all well mixed.
I've got a sample bottle of "Yellow Cake" that came from mount baker Vapor nearly 2 years ago. I keep it to show my friends why shaking is important. I've let the bottle sit for so long without shaking it that the flavoring and nicotine has become a dark brown sludge on the bottom of the bottle while the top 80% is nearly clear PG/VG mix. I've shown it to friends who I make DIY juices for just so they can see why it's important to shake that juice.
As for aging or what many people call "steeping", that's all a matter of preference. Some do, some don't. Some flavors benefit from it, others don't. You can try a juice right after it's mixed and there is nothing wrong if you like it and think it's perfect. However, if it's not quite right you may want to let it sit and age for a while and see if the flavor develops and is enhanced from the aging. It's all a matter of personal preference and personal taste. No one way is right or wrong.
I've got a sample bottle of "Yellow Cake" that came from mount baker Vapor nearly 2 years ago. I keep it to show my friends why shaking is important. I've let the bottle sit for so long without shaking it that the flavoring and nicotine has become a dark brown sludge on the bottom of the bottle while the top 80% is nearly clear PG/VG mix. I've shown it to friends who I make DIY juices for just so they can see why it's important to shake that juice.
As for aging or what many people call "steeping", that's all a matter of preference. Some do, some don't. Some flavors benefit from it, others don't. You can try a juice right after it's mixed and there is nothing wrong if you like it and think it's perfect. However, if it's not quite right you may want to let it sit and age for a while and see if the flavor develops and is enhanced from the aging. It's all a matter of personal preference and personal taste. No one way is right or wrong.