To be precise, one hour 8 minutes and 16 seconds, beyond which, the user can not erase messages. That's a decent chunk of time to delete a message and send a new one if you discover you made a mistake, but recently, WhatsApp significantly increased that limit. Fortunately, WhatsApp users have had about seven minutes to delete messages they've sent, but now they'll have even longer: one hour, eight minutes, and 16 seconds.
Nevertheless, having a grace period of one hour can prove beneficial especially to those who want to erase past messages that may be misconstrued or incriminating. This time limit was decided in case the recipient (s) of the message that is being deleted does not have their mobile device on. Meanwhile, rival messaging app Telegram gives users 48 hours to unsend messages. This ensures that nobody can tamper with the feature to delete messages for everyone. This change was also applied to recent WhatsApp for iOS and Windows Phone updates.
To delete a WhatsApp message, all the sender needs to do is hold their finger down on the message until the option to "Delete" pops up. The app had a flaw though, allowing people with modified versions of the app from third-party sites to delete messages as far back as three years.
You will not be notified if deleting for everyone was not successful.
There's no word on if this quoted-text workaround will be solved by WhatsApp at some point in the future, so for now, you still have to message with some caution. But once, the set time has passed, there is no way to delete messages for everyone.