I have $109 on a travel fund that expired 6/9/18. I can't fly before then. Can I book a flight for a "trip" from 6/4-6/9/18 which will now be 399.98 due to close dates,. Use the $109 and pay the balance with a gift card. Then cancel the entire trip on 6/7 and get a new travel fund for $399? Thanks!
If you do, the entire $399.98 balance, including the new money from the gift card, will all expire on 6/9.
Whenever you use travel funds to make a new reservation, that reservation takes on the earliest expiration date of any travel funds applied.
If you definitely aren't able to use the funds prior to expiration, your only other option would be to request the funds be reissued once they're expired. The fee for this however is $100, meaning that, in this particular situation it's not really worth it.