Definition of "heyday"

Must your hot ytch and plurisie of lust, The heyday of your luxury, be fedd Up to a surfeite, and could none but I Be pickt out to be cloake to your close tricks, Your belly-sports?

c. 1626 or 1629–1633 (first performance), [John Ford], ’Tis Pitty Shee’s a Whore […], London: […] Nicholas Okes for Richard Collins, […], published 1633, Act IV

"Heyday, Miss Morland!" said he. "What is the meaning of this? I thought you and I were to dance together."

1798, Jane Austen, Northanger Abbey

"Come follow me, my wags, and say, as I say. There's no riches but in rags; hey day, hey day, &c."

1600, Ben Jonson - Cynthia's Revels

Bass. Heydey! good words, good words, I must beleeue'em And be a Coxcombe for my labor.

1633, John Ford, The Broken Heart, act IV, scene i, page 252

Here Jones, having ordered a servant to show a room above stairs, was ascending, when the dishevelled fair, hastily following, was laid hold on by the master of the house, who cried, “Heyday, where is that beggar wench going? Stay below stairs, I desire you.”

1749, Henry Fielding, The History of Tom Jones, a Foundling, volumes (please specify |volume=I to VI), London: A[ndrew] Millar, […]