Hey, Srgrounds. When I got my first bottle, it was 15 ml 80 pg/20 vg house blend, with zero extra shots of flavoring. And man, it tasted good right out of the bottle. But I noticed a dramatic color change as I used it... it went from a very clear color to a dark amber hue. And when it reached that amber color, it tasted even more delicious.
I then learned to steep it. So, yes, to answer your question, I do steep it. I keep it in the corner of a cabinet, away from the sun and any heating vents, for at least three to four days after receiving it (each bottle is made fresh so it doesn't steep at MBV's premises). I shake it vigorously for as long as I can manage as often as possible, too. Usually one of the nights I'll unscrew the lid and leave the bottle open to air.
As for flavoring, my last order was for 3 extra shots of flavoring, and it's beyond delicious. I would say, if you like what you get and don't feel the need to up the flavor, you don't have to. But if you want that buttery sweetness to linger on your tongue, go for the extra shots.
Hope that helped.
EDIT: Forgot to mention, I've never had their 50/50 blend, just their 80/20, so that may affect the flavor.