Can a long life bag be used in the CTM 36 Planex when sanding with my Planex Dust Extractor?

No, the long life bag should not be used when sanding plaster dust with a PLANEX system. 
Because plaster dust is so fine, if the long life bag were to be used, this extremely fine dust can clog the pores of the bag quickly therefore reducing the effectivesess of the dust extraction.

Festool recommends using a
CT 36 Autoclean Dust Extractor when working with plaster and concrete dust with the open plastic bag.