The airlines have a relatively consistent fiscal year as far as liquidating premium inventory is concerned. Although January is known to be a clearance month to fill empty wide-body jets, the most aggressive pricing is done on the so-called Travel Tuesday, the day after Cyber Monday. In order to get business class flights sale, it is recommended that the flight not be booked too far in advance, the optimum period to book an international premium cabin is usually 60 to 90 days prior to the flight, when revenue management units will sell the unsold flights to the discount market.
https://askforairlines.com/blog/business-clas