Some travel insurance policies base benefits on whether or not the entire cost of the trip was insured or not. If you want travel delay covered in the event you miss your flight home for a covered reason, you at least need to cover the cost of the cruise, the airline tickets and have the date you leave home and the date you return home.
Read any policy you're thinking about buying carefully. I lost $1,400 because of a clause in our policy which stipulated any trip interuption/delay had to be caused by very specific circumstances. I've since found policies that aren't as restrictive and won't go back to the company that denied our claim. They might be a good company but to many restricitions give them to many loop holes to deny a claim.
At the moment, I'm favoring CSA and Travelex companies. CSA will cover pre-exisiting conditions if purchased within 24 hours of FINAL payment. Most won't cover pre-exisiting conditions unless it's purchased within 15 days of the initial cruise deposit.
There's a lot of information available about several companies at
http://www.insuremytrip.com
