I try to indulge in Vitamin N only once per pipe. I too have the occasional lapse.
As a former cigarette smoker, it's part and parcel to develop the kinesthetic memory to puff then inhale. I have to consciously resist the desire to do so.
If I decide to inhale it is always on the true light only. IMO if there are flavor additives they would be released into the smoke most intensely on the char, I have no evidence to support that opinion. It's just that, an opinion. Besides; I don't want to do anything that would interfere with that first excellent taste of a freshly lit blend.