Crossing the Dark Sea of Darkness

This shouldn't be very spoilery, but the main reason I'm asking is because of N!obE, so it might get a little spoilery in comments???

Does anyone know how long it takes to cross the DSoD? For the longest time I've had it in my head that it takes about eight weeks (and I was sure I read it somewhere in the series), but now I'm doubting myself. I'm particularly concerned because I've used this bit of information in multiple fanfictions, and I would rather use as little noncanonical information as possible sooo... 😅