Happy to be corrected but my impression is that steeping is about the flavours blending, so in a sense the warmer the better for reactoons/fluidity but obviously thats not best for longevity of nic etc so a balance is called for, i steep at room temp mainly, zapping them with a mini whisk to mix and oxygenate every... most... some days until i think its readyish, then bottle some for immediate vaping and move the rest to the cooler place for storage.
I must say im thrilled to be getting into mixing again, kinda got out of it when a vape shop opened nearby and spent lots on elements and the like but time to rein in the cost and be more creative, waiting for my concentrate of mince pie and brandy from chefs now, along with a shitload of othef stuff including 30ml of welsh conc.