Note 293 — LII (Q FR I, 2)
Evelyn S. (Evelyn Shirley) Shuckburgh translation
ἅπαξ θανεῖν, perhaps "Better to die once for all than give in to every unjust demand." The editors quote Æschylus, Pr. V. 769:
κρεῖσσον γὰρ εἰσάπαξ θανεῖν ἢ θὰς ἁπάσας ἡμέρας πάσχειν κακῶς.
But I don't feel sure that this is the passage alluded to.