When using network rendering I have noticed that the regions for my animations are always completed long before the frames; for example, the 250-frame animation I submitted today had completed all 257 regions in approximately 30 minutes but the frames look like they are going to take almost 90 minutes longer before the animation is ready for downloading. During this 'additional' time the slave machines display the 'rendering' status but no individual progress is shown as all their assigned regions are already complete.
Can somebody explain this phenomenon to me? Why do the regions complete so long before the frames? Are the slaves actually working after all of the regions are complete?