I moved from a call center where length was a KPI to one where it is not a KPI, and it makes a world of difference in the pressure/health of the office environment (and thus better outcomes for customers)

It is far better when call length is not a KPI. I would never go back.

IMO, if call length is a KPI, it's a key indicator that the company isn't willing to hire enough agents and is trying to apply pressure to shorten calls for purposes of coverage.