Do you guys think a wax warmer + frequent stirring would work for steeping a juice quickly? I hate to say it, but i'm impatient.
Any amount of heat reduces the steeping time. On a molecular level, all that heat does is it makes the molecules move faster. So whatever happens when you let a juice sit for a while and "steep", it happens more quickly when you apply heat. Lets say it takes 1 week to steep your juice to perfection at 20 C, it takes a fraction of that time to steep it 40 C (lets say 3 days). You should be cautious to not heat the juice to high temperatures (no one really knows what's the ideal temperature, but around 100-115 F seems to be the general consensus), because as you apply more and more heat certain unwanted chemical reactions can take place.
Ya, thats right. As a rule of thumb a chemical reaction doubles it's speed when temperature is raised by 10°C. However, as /u/Ternopil mentioned, some reactions need a certain activation energy. That means that possibly unwanted reactions don't happen on low steeping temperature, but will on higher temperature.
TL/DR Yes heat helps. But heat also implies the risk of unwanted reactions.
And yes, I heat steep my liquids. Unfortunately, they taste better when steeped the old fashioned way.
Heat + agitation will change how your product steeps. Note that "change" is not the same as "speed up"; If you heat a juice too much you will change its flavor and in some cases its a bad change. I only mildly heat my 500 to 1000ml batches, no more than 105° F with vigorous agitation. This helps homogenize everything too, by lowering the viscosity of the VG. The only volatiles and evaporants that I think about are alcohol based flavorings if the recipe called for any.