I retired from USPS on or before January 1, 2025, and have Medicare Part B coverage. Do I need to keep my coverage? What about my spouse? 

Maybe. If you are an annuitant on or before January 1, 2025, and you are enrolled in Medicare Part B on January 1, 2025, you are required to remain enrolled in Medicare Part B to continue coverage under PSHB, unless you are eligible for an exception. 

Also, if you are the spouse of an annuitant who is already enrolled in Medicare Part B, you are required to enroll in Medicare Part B when you become entitled to Medicare Part A, unless you are eligible for an exception.