When do the unmarked Fuji E6 mailers expire?

The older Fuji slide mailers have no expiration date on them. Does this mean they won't expire?

Fuji's contract with Dwayne's expires on 31 December 2009, so if Fuji renews or finds another place to do E-6 for them, then they will be fine. Though, I, for one, shall use all of mine (somehow) before 31 December 2009 and see what happens in 2010.