^Yes…and no
Yes, you can use earlier CFA material, since the syllabus doesn’t change *too much* each year. But no, I don’t think you need to start studying for next year’s exam…today.
Everyone differs in how much time they need to prepare for any particular level. While the general rule of thumb is 300 hours, based upon my own experience I would recommend the following::
* Level I –> ~250 hours (4-5 months)
* Level II –> ~400-500 hours (6-7 months)
* Level III –> ~400-500 hours (6-7 months)
IMO, supplemental material (e.g., Schweser) works for Level I and Level II, but CFAI syllabus is better for LIII.