Assume 6 seasons for the entire series if you're lucky. Yes, I'm cheering for an early cancellation because I think the whole thing ended up a ruined pile of shit, but realistically, if they got 8 seasons it would be remarkable. Most story arc series finish by 5 or 6. Assume a first season of 10 episodes at most. That means you have to do the following:
Season 1 - Eye of the World, Great Hunt
Season 2 - Dragon Reborn, Shadow Rising
Season 3 - Fires of Heaven, Lord of Chaos
Season 4 - 3 of those crappy later books (7-9)
Season 5 - everything up to the last book "trilogy" (10-part of 12)
Season 6 - Finish
If you only have 5 seasons then I would smash the later books even more densely into 4 and 5 and leave 1-3 at 2 books per season.
ἡ δὲ κἀκ τριῶν τρυπημάτων ἐργαζομένη ἐνεκάλει τῇ φύσει, δυσφορουμένη, ὅτι δὴ μὴ καὶ τοὺς τιτθοὺς αὐτῇ εὐρύτερον ἢ νῦν εἰσι τρυπώη, ὅπως καὶ ἄλλην ἐνταῦθα μίξιν ἐπιτεχνᾶσθαι δυνατὴ εἴη. – Procopius
Ummaka qinnassa nīk!
*MySmiley*