First thing:
Delayed arrival is only on testing at the moment.
Beyond that: The option should always appear unless you are one hour away from the destination. It should not appear if you are one hour away, and you should not get sucked into battle. If either of those happen, that's a bug, please report it.
If you have more hours than the time it takes to get to the region after factoring in all the scouts and infil delays and such, then you get set to one hour away, so you can't delay arrival again.