It all depend on the paper you are sitting for. For example, BPP/Kaplan for P4 is still valid for December exams because the syllabus has not changed. Whatever paper you are considering you have to confirm that the syllabus are still the same because for example there is a new IFRS that will affect people sitting for P2 or P7 which is IFRS 9 Impairment of Financial Asset and Liability.