I'm sorry, but you have this backwards - the nine hour response window is just a means to ensure the pilot is able to meet the NLT 3 hour requirement. The NLT 3 hours is the contractual requirement - NOT the nine hours.

From the Scheduling Reference Handbook:
"This effectively means a long-call pilot could turn off his phone for as long as nine hours, provided he then checks his messages and/or schedule in order to comply with the above requirements for acknowledgement."

In other words, as long a pilot checks his schedule every nine hours, he will be ABLE to comply with the NLT 3 requirement. It does not mean that there is actually a 9 hour window. The ONLY requirement is the NLT 3 hours - period.

Now, would an arbitrator agree with the reasonableness of waiting right up to the 3 hour limit? I have no idea, but I'd hope so since it's the only contractual limit actually we have.