Hal went insane in 94, maybe late 93. Remained Parallax until Final Night in 96/early 97, where he died. And yeah, I think there were a couple time travel stories that happened afterwards, where Zero-Hour era Hal would pop up to cause trouble, including young, rookie Hal coming into the present in Green Lantern #100.
Overall, Kyle held the title of primary Green Lantern for about eleven years, from Emerald Twilight to Rebirth. But Hal was the Spectre for a good chunk of that time.
As for Donna, I dont think her turn as a villain will last more than a storyline or two. If she's still a villain when the Finches leave, it'll be fixed by the next creative team. Or she'll be ignored and forgotten and eventually replaced by a different version with no ties to the person who just climbed out of a cauldron.