Heat, Light, and Air are the enemies of eLiquid.
There is no circumstance where light is good - it degrades the nicotine in the liquid.
Heat can be applied in controlled ways to decrease steep time, sometimes with undesired results. It's not that it's not possible to decrease steep time with ultrasonic cleaners, hot water baths, or the warm rice method - it's just that your "playing with fire" if you don't know what you're doing. Some people have used heat steeping with (they say) great results... and then some people say "they followed the process" and it ruined the liquid. This leads me to say "why take the chance" - I generally recommend people let time take it's course and resist the temptation to expose liquid to heat.
On the air front - we have taken care of the vast majority of the "breathing" for you so even the above so any additional exposure is "above and beyond". This is a judgement call, based entirely on the liquid in question. In the case of the "core flavors" in our our lineup (IE, the ones without "SR" in the name) - I would discourage protracted exposure to air since the liquid is adequately pre-steeped - all that remains for you to do is periodically (once a week or so?) pulse the bottle, shake, and wait. Once a week will more than suffice, and no protracted period of breathing is really required. In the case of the short-runs that are more recently mixed, they can benefit from 12-24 hours of "breathing" - followed by the same "once a week pulse and shake regimen" outlined above. Obviously the more air that penetrates the liquid, the faster it will steep (oxidize)...
Although I personally experience minimal flavor degradation even over protracted periods of air exposure (YMMV!), we still very much encourage you cap your bottles and keep them away from light, heat, air, children, and other vapers who will hit your stash!!