I used my United Airlines ETC (with expiration date 5/6/2025) to book UA Standard Economy international ticket (SFO – FRA) with travel dates within the ETC's valid period (begin travel by 5/5/2025). Now I want to use "Change Flight" to change the ticket’s travel date to after the ETC's expiration date 5/6/2026 to match my actual travel dates. Does this "Change Flight" workaround still work? Can I book a “dummy” ticket with travel dates within the ETC's valid period and later use "Change Flight" to push the travel dates out to after the ETC’s expiration date?