Homologous recombination (HR) of DNA double-strand breaks (DSBs) is restricted to the S-phase. This suggests that HR as repair pathway has evolved specifically to deal with DSB that arise during replication (for instance from an SSB, at a crosslink, or aome other problem at the replication fork). In most cases, the opposite DNA strand has already replicated at the time the repair starts. There is no need to search for homologous duplex over the whole nucleus -- it is already available within the same replicastion fork. This is a simplified view, of course :)