Great question. Your Platoon Sergeant can certainly set a goal for you and your platoon to obtain. However, he cannot make it mandatory. In addition, taking an APFT every other week may injure Soldiers, set Soldiers up for injury, and cause increasingly poor APFT performance from overuse. FM 7-22 specifically addresses over-training Soldiers and AR 350-1 specifically discusses physical fitness, including the APFT test. More specifically AR 350-1 Appendix G-9 a(2) states:
Commanders may establish unit APFT mission related goals which exceed Army minimum standards. However, individuals must be aware of these goals and be able to achieve them safely through the use of normal training time and adherence to the principles of conditioning outlined in FM 21–20. Personnel who meet Army minimum standards, but fail to meet unit goals, may not be punished or disciplined. However, they may be required to participate in special conditioning programs which focus on overcoming a weakness. Commanders who establish higher goals should do so because their unit missions require Soldiers to be more than minimally fit. Like-units with identical missions (companies within battalions, battalions within brigades) should have similar standards. Care must be taken by the chain of command to ensure unit goals do not arbitrarily replace Army standard.