1. A computer controlled method, comprising: accessing a plurality of coefficient vectors, wherein a respective coefficient vector represents an entity within a persistent virtual environment and comprises a plurality of coefficients, which represent a temporal profile of the entity, wherein the temporal profile indicates the entity's past presence in the persistent virtual environment; generating a player cluster, which includes two or more entities, based on coefficient vectors for the two or more entities; generating a combined coefficient vector from the individual coefficient vectors corresponding to each of the two or more entities; generating a combined temporal profile from the combined coefficient vector, wherein the combined temporal profile indicates presence information for the two or more entities; extending the combined temporal profile into a future time range to produce an extended temporal profile that identifies a set of future time points when the two or more entities are likely to be available; determining, by a computer, a likelihood and a prediction strength associated with each future time point, wherein the likelihood is determined based on the combined coefficient vector for the two or more entities, and wherein the prediction strength is determined based on a merit value that indicates how well the combined temporal profile indicating past presence represents recent presence of the two or more entities in the persistent virtual environment; and presenting a recommendation based on the likelihood and the strength associated with each future time point.