If it's working I see no reason to switch. People say calurpa can "go sexual" and die as part of reproduction/it's life cylce unless you run a fuge light 24/7. I ran a 12 hour fuge light schedule without issue though so I am not sure how true that is/what the actual risk is. Also, switching and introducing chaeto does expose you to the risk of introducing pests (guess that is true of most things you add to the tank haha)
I could never keep chaeto long term even with a powerful kessil fuge light. Nutrient was never the issue - heavily stocked. Maybe something about iron/mineral deficiency that chaeto sucks up?
Had much better run and longer term with caleurpa.