Please make sure before you go on your cruise, if you are elderly or have health problems...call your insurance carrier and find out if they will cover you if need be. My grandmother has medicare, and they will not cover her because the ship is not US registered. Please be aware. It was very costly! The diamond is registered in Bermuda.
One should always get trip insurance. There are many good policies that can be purchased on line. I've had good results with Travel Insured International and I'll find out soon about Travel Guard. If one purchases the insurance anywhere from 10 to 14 days from making their initial cruise deposit, pre-conditions are waived. On our recent trip we ran up $430 in medical bills on board and we expect them to be covered by Travel Guard. Another plus with trip insurance, there is no deductible or co-pay for medical.
Another thing to note. If you are on Princess (not sure about other lines), the Princess Insurance is priced according to trip, not age.
When my mother, 87, and I, 58, went on a cruise together, I bought Travel Guard, from InsureMyTrip.com, but it was much, MUCH less expensive to buy the Princess Insurance for my Mom. We had the same coverage. Also, if you are Platinum or above, on Princess, you will be upgraded to their Gold coverage at no extra charge when you buy their insurance.
Does Princess' Gold coverage include more than just the cruise. If so, it may have changed over the years. In the past, purchasing the cruise lines insurance was like buying the sleeves of a vest, they only covered you for the cruise itself, something they usually resold. And the amount covered was only a portion of the cost until one got closer to the sail date. Also, if I recall, if one didn't book their air with the cruise line, that wasn't covered by their policy.
What one needs is not only an insurance policy that covers the cruise but one that covers the entire trip including the default of carriers. For example, AAA sells a travel policy but their fine print shows they don't cover default of any foreign airline and many domestic airlines including a big one like United. One should have both trip cancellation and interuption insurance - we had to use this when there was a death in the family back home while we were at sea. Coverage for delays and lost luggage and especially medical. One can get a less expensive supplemental coverage for medical where your own insurance is primary. Then, if it doesn't cover anything out of the US, they'd still pay for everything.
It is true that the older one is, the more expensive the on-line insurance is.