It's my nighttime thing, before sleep.
I have very poor vision and at the end of the day my eyes are tired. It's tough to read but I'm not ready to sleep. So I lay in bed in the dark and listen to the books.
(I can never drift off when the Nac Mac Feegle are talking, though. Hardest I've laughed in a long time was recently as I listened to the Feegles arguing with each other when they were masquerading as human body parts in Hat Full of Sky. Stephen's translation of that is nothing short of brilliant.)
I'd very much like to listen to Unseen Academicals and read it at the same time. I've only listened to the book so far, and there are a few things I don't quite get but I bet reading and listening at the same time would bring a new element to the experience.
Something for a rainy day, it would be quite nice.

Nullum magnum ingenium sine mixtura dementiae fuit. -Seneca