Item 3 from Terms and Conditions on my bump voucher reads as follows:

3. TRAVEL ON SUCH TICKET IN NOT VALID UNTIL TWO DAYS AFTER THE DATE OF VOUCHER ISSUANCE/ AND TRAVEL MUST COMMENCE WITHIN ONE YEAR OF THE DATE OF VOUCHER ISSUANCE. ONCE ISSUED/ THE TICKET OR UPGRADE IS NOT TRANSFERABLE AND NONREFUNDABLE

They might have been a little flexible in the past in enforcing the "travel must commence within a year" clause. But in my experience at Federal St. CTO, Boston these days they go only by the book. No exceptions are granted and I for one like it.