Not only that...but I contacted Support regarding it to confirm how the eligibility works...and got a non-answer.
The below is in response to if someone in a similar situation as myself(buy 180 days sub at a time, my last payment was in April - by my calculations it won't be up until Oct):Thank you for contacting SQUARE ENIX Support,
Please note the Flight of the Falcon Campaign started on July 1, 2017 and ends on September 30, 2017. Game time purchased outside of the campaign period may not meet the requirements for the Campaign. If you have remaining subscription time that was purchased before the campaign period, or you have an active recurring subscription, we will calculate any remaining game time available as of Saturday, July 1, towards the campaign.
The requirements for the campaign is the registration of Final Fantasy XIV: Stormblood and the purchase of a subscription of at least 90 days during the campaign. We apologize for any confusion. Please visit the FINAL FANTASY XIV Lodestone for more information:
http://na.finalfantasyxiv.com/lodestone