Ae can segment image sequence renders to a specific number of frames, according to Preferences > Output > Segment sequences at...
For example, if the frame rate is 29.97 or 30 fps, checking that box and entering 450 frames will give you 15 second splits. Ae will create a separate folder for each segmented image sequence.
Create 120 15-second null layers, make them guide layers, then use the Sequence Layers keyframe assistant to sequence them end to end in your timeline.
Use Christopher Green's awesome Queue Comp Sections script [link] to queue up separate renders for each. Send some money his way via the donation button on his site because his script saved you so much time.
Ae might not be the best place to do this. Perhaps an encoding application would be better. ffmpeg, for example, has a segment feature [link].