These repetitions of a simple εἰμί with a πέλω thrown in seem unusual for Homer, though the assonance doesn’t. Maybe to emphasize μήνι ? Beginning of book 12:
τὸ καὶ οὔ τι πολὺν χρόνον ἔμπεδον ἦεν.
ὄφρα μὲν Ἕκτωρ ζωὸς ἔην καὶ μήνι᾽ Ἀχιλλεὺς
καὶ Πριάμοιο ἄνακτος ἀπόρθητος πόλις ἔπλεν,
τόφρα δὲ καὶ μέγα τεῖχος Ἀχαιῶν ἔμπεδον ἦεν.
Meanwhile the ὄφρα and τόφρα reverberate with the τάφρος (“ditch”) of previous lines, and, phonetics or not, it’s an unusually prospective passage.
.i`` * ^ / . . . . . ` `~ 