Expiry of Amex PE Upgrades

First post - found the forum invaluable so decided it was time to join.

I've earned 2 PE upgrades on my VA Amex which have a 12 month expiry. Does this mean I have to FLY within 12 months to use the upgrade or simply book within 12 months but perhaps fly at a later date beyond 12 months.

Flying PE to Antigua in November so should have enough miles on my return to book 2 reward flights and use the upgrades.

TIA for any advice.

No the booking has to be made before expiry of the vouchers and therefore the flight could be made up to 11 months after they expire.