Dogs in heat are obsessive about intercourse, it occurs when they are ready to conceive. 2LiveCrew shares this same sexually obsessive mentality, but without the instinct to procreate as the driving force.
Re-ups are when the new "package" of drugs come in. Wayne is saying they are like birthday parties, because they are so popular (and the drugs are like a gift). He adds "no room to park cars in the garages" due to high volume of interest in his re-up