Yes, yeast flocculates at low temperatures and when there is nothing left to ferment, this is why your beer becomes clear as fermentation finishes.
The yeast will not stay in suspension if there is nothing to ferment, or if the temperature is too low for the yeast type.
I ususally direct everyone who is new at using liquid cultures to
Mr. Malty this is a very informative site, and will teach you all the basics you need to know about liquid yeast, and their proper use.