With Season 3 Valhalla, all the offers were altered to be available for the entire duration of the event.
You can go back on Day 4 and purchase the Day 1 offer.
Please modify this for all events. mAtlantis, Challenges, Costumes, Legends, etc… and possibly the seasonal events although I understand this one may be a bit more work. I think you’ll find this will give a revenue increase and a happier player base.