Accrued leave is a liability on the company books, if you leave they have to pay out against it. Company policy is that no-one (and that includes flying crew) should accrue and carry over more than five days at the end of the year. If you have not used it, that is your own fault unless the company has denied you an application. Forced leave, or rather asking you to avail of your leave as soon as possible, is an offensive (i.e. reducing liability) step for any company to take in circumstances where it is warranted. They could always take your leave balance off you if you did not follow policy; I would suggest you make the most of it and take it before they actually do decide that you have forfeited it.