Nice, clear, simple copy in ClarisWorks from 1997:

No “Maybe later.” No “Not now.” Thirteen characters. Now, Later, Never.

(Can’t help but notice that Esc and ⌘. – the classic Mac’s equivalent of Esc – still map to Later, however. Also, this breaks the rule of button copy being fully comprehensible without having to read the surrounding strings first, perhaps most well-known as the “avoid «click here»” rule. Never Register/​Register Later/​Register Now would solve that problem, but wouldn’t look so neat.)