Which stage of Product Life Cycle is most difficult to handle and why?

I believe the “sustaining” phase (AKA the “maintenance” phase) after product launch is the most challenging. Product development can be done with particular “objectives” , and once the product is launched it is extremely important to ensure the product is sustained the manner it should.

This is the critical phase in PLC that will ensure the product does not derail from where it should be heading.

The “sustaining phase” ensures that the product lives up to the demands of the changing market needs. And knowing when to exactly decommission a product is part of sustaining efforts.

Thoughts welcome!