Look if the options favour buying discount J over T+ or Lat fare, take your COS bonus and buy up to J. Don't look the gift horse in mouth.

The only people I feel sorry for are my work mates that go to Aruba. Their client will not reimburse J, even if they prove J is less price than Y (which to Aruba it often is with a discount coupon). So my mates are stuck flying in Y due to client expense reimbursement practices.