In Les' book, he breaks an indicated 4 second exposure into 32 exposures at 1/125, so it's more what I'd consider multiple short exposures in that particular instance. Of course you can go with any combination of multiple exposures of any length that sum to the proper exposure length, and get a variety of effects in doing so.
Originally Posted by MikeK
The best way to get what you want, as always, is to make some tests and see what gets you where you want to go.
The longer the exposure, the "silkier", up to the point of overexposing.