Liquid improves with age. the aging process speeds up with more air, heat and UV light.
Typically clearos heat up your liquid, allow light through (as they are generally clear) and you add more air through them as you draw on them. So you're effectively speed steeping e-liquid in a clearomiser and most e-liquid on the market isn't fully steeped when you get it.
Also over time the coil and wicks 'bed in' and improve with age. You often get a 'brand new coil taste' from atomisers. this is sometimes dirt on the coil or wick, maybe some kind of coating on the surface of the wire that burns off as you break it in, Sometimes if your hands were greasy when you install a new coil the wick will soak up (it's a wick, that's what it does) any traces of liquid on your fingers, or maybe the person in the clearo factory that put the clearo together didn't have the cleanest hands in the world.
