Honestly, most of the cases that I can think of where you want to move a mechanism this slowly would also be high load applications. As an example: thinking about 2019’s endgame HAB3 climb, many teams had some sort of arm off the front of their robot that would grab the top of the hab and pull up the front of the robot. That could be accomplished with 90-ish degrees of rotation (so ~3 seconds with this 977:1 reduction), but the load that you are lifting is quite large and the lever arm is also quite large.
These motors are not ideal for these type of applications for the following reasons:
The PG motor is not really that strong. so even though the torque is decent with this 977:1, it does not compare to a similarly geared MiniCIM or NEO or 775Pro.
Actuating a high load arm through a hex joint is probably not the best design practice given the high loading at such a small diameter. It is usually better to accomplish the final reduction with a large diameter gear or sprocket that can be directly attached to the arm so that the load is carried by a bolted joint at a large diameter from the pivot.
So, you would want to limit this gearmotor to lower load applications and honestly, I can’t think of any that would require motion this slow.
Having recently diassembled some of our older PG188s and PG71s it is easy to see how you could just keep stacking the stages and just cut the extrusion that forms the outer case to longer lengths. So, there are no new parts here (just re-configuration of existing parts). So it is an easy configuration to offer. Who knows, maybe applications will come up where this will be the prefect part for the job. But, I think those cases will be rare.