Join Date: May 2006
Location: New York, London, Sydney
Programs: United GS/2MM, DL*P, VS*G, AA*EXP, Avis CHM, Hertz Platinum, Sixt*D, HH*D, HGP*P, Starwood*P
Posts: 9,847
Normally, refundable tickets expire within a year, but can be "revived" for $100 or so by the refunds department.
Not sure if there are any complications because of the fact that it was partially-used, never ran into that situation myself, but I'd suspect it shouldn't change the fact.