In a remarkable judgement (Thiruvengada Pillai vs. Navaneethammal and Anr. ), the Supreme Court held that the stamp papers can be used after a period of 6 months from the date of purchase etc. The Indian Stamp Act, 1899 nowhere prescribes any expiry date for use of a stamp paper .
Section 54 merely provides that a person possessing a stamp paper for which he has no immediate use (which is not spoiled or rendered unfit or useless) can seek refund of the value thereof by surrendering such stamp paper to the collector provided it was purchased within the priod of 6 months next preceding the date on which it was surrendered.
The stipulation of the period of 6 montsh prescribed in Section 54 is only for the purpose of seekign a refund of the value of the unused stamp paper and not for the use of the stamp paper.
However the above interpretation may have to be checked with the state stamp acts for their applicability.