Anybody can retire and/or quit when they want to. But why force one to quit just because of their age. As long as one keeps passing his/her flight checks, flight physicals & and can still do the job why not continue flying commercially until he/she reaches the age of 65.
For what its worth the Nigerian NCAA has confirmed that commercial pilots can continue flying PIC until they reach the age of 65 two crew. The second pilot must be under 60, there is no 120 limit on the age of both.
And also the German Luftfahrt Bundesamt (LBA) allows single pilot commercial flying until the age of 65.
Some of us really like our work flying so why quit early!