On ticketless travel funds, you have one year from the date of original purchase in which to complete travel, and they are (now) tied to the same customer for which they were originally ticketed. In your example, you would need to complete the travel by October 3.

It's been reported here that the following may be changing, or recently changed (as noted), but the policy for extending is: within 6 months of the expiration date you can pay $50 (may now be $75) to have the funds reissued as a LUV voucher, which is good for an additional 6 months from the date issued, and (possibly) can be used by anyone. That means you would have until the following April 3 to call Southwest for reissue, and the voucher would be good until the following October 3.

It's probably best to not expect those dates to be exact; I'd call a few days prior if I were you. Also, since it seems things are changing in regards to this policy, you should contact Southwest (again) and ask for verification, and document everything. It might be a good idea to do this through email or a written letter, so you have a paper trail.