1. never-ending (?1592)
2. never-ending from 1667 (Paradise Lost), never-erring from 1679
3. One of the current OED lexicographers has recently reviewed OED3’s treatment of Shakespeare over a smaller sample of words attributed to Shakespeare as first user in OED2 (117 words over P…Ra), to show that nearly half have been antedated in OED3; see Giles Goodland, ‘Shakespeare’s First Citations in the OED’, in Stylistics and Shakespeare’s Language, ed. Mireille Ravassat and Jonathan Culpeper (London and New York, 2011), pp. 8–33. In the same collection, Ward E. Y. Elliott and Robert J. Valenza are similarly sceptical about attributing spectacular lexical productivity to Shakespeare (‘Shakespeare’s Vocabulary: Did it Dwarf All Others?’, pp. 34–57)
4. The Use of Literary Quotations in the Oxford English Dictionary