The requirement may not expire, but all FMS requests expire. They are not permanent. That's because the pricing changes after the expiry date. So, at best, 1 year.
If after nearly 5 years there's been no deal, then it's obvious the UAE has allowed the FMS request to expire. Which means, the process has to start from scratch again.
And to date, the UAE has only signed up for the F-16 upgrade deal.
Personally, I think the UAE is threatening to sign up with the Russians for the LMFI if the US doesn't sell them the F-35.
https://fas.org/asmp/campaigns/MANPADS/Chapter 5 FMS Case Development.pdf
The current contract for this item expires on [insert date] and an LOA must be accepted by [insert date] so that options can be added to the current contract.