You can try now! Again, reports are Amex is being really generous with their Platinum retention offers right now. Might as well try while the gettin’s good, since you can technically cancel your card in about a week. Mention that your cardmember anniversary is coming up in the next week or so, that you’re deciding whether to keep or cancel the card, and wondering if they have any offers that’ll help you decide to keep it for another year. They may give you the usual talking points about spend, sell you on the card benefits, ask about your other cards; just have some good responses ready and be insistent. If there’s an offer on your account, they have to read it to you. If there’s nothing yet, wait til it’s been 1 year, and again when the AF posts, and maybe again just before the deadline to cancel. Good luck!