When the physical Apple Card was announced, we didn't know when it would expire, but now that Apple is sending Apple Card soon-expiring emails, it seems like it's 5 years (the card was originally launched in August 2019). According to the email, the customers will recieve new replacements in 2 weeks or less from yesterday. A shipping label will be included in the replacements so the old cards can be recycled, and Apple advises these launch-day customers to activate their replacement right after it arrives; the old cards will stop being usable after expiration this summer. The email says "We’re sending a replacement titanium card to your billing address so you can continue to use it at physical locations. Remember, even without a physical card you can always use your Apple Card at any location that accepts Apple Pay. Your new titanium card will be shipped within 2 weeks from the date of this communication.
You can continue to use your titanium card until it expires or you activate the new one. You can still use Apple Card with Apple Pay and your virtual card number to shop at merchants that don’t yet accept Apple Pay by typing in your number from Wallet or using Safari AutoFill." The Apple Card website is accessible here.
By Leo