It depends on you and your workload.
If you decide to take Coaching Mastery and Business Mastery at the same time you will be finished both certifications in 6 months. If you choose to take the programs one after another you will finish the certifications in 9 months.
Its recommended that you have at a minimum 5 hours per week if you are taking both programs at once. If you have less than 5 hours per week it's recommended that you take the programs one after the other.