No time restrictions on use. Just to remind you the spouse pass is strictly for your spouse, it's not a companion pass for anyone to accompany you. I think previously there was the impression with some people that they could offer the person next to them in the queue for the bus a free ride.
Also, earlier in the thread it was stated categorically that the free travel pass works on all Aircoach services, I'm fairly certain that's not the case, you should check with them and any other private operator in advance as not all services accept the free travel pass.