My suggestion for those who are planning to apply for study permit for January 2019 intake apply for study permit at least 4 month in advance no later than end of September. SDS is not in this category, but even for SDS give at least 60 days. If you apply later than those days, do not book your flights early or at least book only refundable flights. Your application could be delayed for various reasons. My application is still under review and it has been more than 90 now. I did mistake booking non-refundable flights early and lost ample amount of money. I do not want you do the same mistake.