Downsides to trying to make three parties in one night:

1. You spend half the night in a car, drunkenly squinting at a road map and saying "Is this Ord Street?"

2. You either need to do a costume change en route or risk looking alternately ridiculously overdressed and underdressed.

3. You only recall the next day why it's a bad idea to go from champagne to suspicious (though delicious) rum punch to some fancy berrylicious cocktail and then back to champagne.