The short answer is, it seems you'll be ok.
It's hard to prove the opposite, because there's little detail about the validity of this document anywhere.
From searching through EU embassy websites and EU legal documents, they all claim to recognize the document but few specify what validity is accepted in case you don't need a visa. Denmark for example, only cares that you're a legal resident of Malta, Italy considers it equivalent to a passport.
23. Holders of valid travel documents issued under the Convention of 28
September 1954 Relating to the Status of Stateless Persons, provided that
the travel document has been issued by one of the EU/Schengen States
Holders of valid travel documents issued in accordance with the Convention
of 28 September 1954 Relating to the Status of Stateless Persons may
enter Denmark without any visa, provided that the travel document has
been issued by one of the EU/Schengen States and that the holder is a legal
resident of the EU/Schengen State that issued the travel document.
Belgium mentions it only need to be valid.
Condition générale: l'intéressé doit être en possession d'un document de voyage en cours de validité, délivré conformément aux règles [...], de la convention du 28 juillet 1951 relative au statut des réfugiés[...]. Les documents de voyage doivent contenir une autorisation de retour ayant une durée de validité suffisament longue.
According to the 1951 Convention, the travel document guarantees your right to return to the issuing country, in this case Malta, for the entire duration of the validity period.
1. Each Contracting State undertakes that the holder of a travel document issued by it in accordance with article 28 of this Convention shall be re- admitted to its territory at any time during the period of its validity.