Just chatted with a CSR as I request to ask about the expiration date of my store credit, she informed me that the expiration date has been extended to 1/1/2020 and this applies to everyone that bought the Pixel 3a there.
This was the original post:https://slickdeals.net/f/13067110-pixel-3a-100-google-store-credit
and it was set to be expired 8/31/19. If you are not still not sure, just check with a Google support.
Great deal for holiday season shopping or if you want to get a Pixel 4!