We always buy insurance and use travel guard. We buy within 14 days to be sure we have coverage for any pre-existing conditions as we have two special needs children
My question about ABD is when they purchase their insurance. On
DCL my understanding is that insurance is not purchased until final payment and that then changes the pre-existing clause. For us, we are already a couple thousand into airfare even if our deposits are refundable by the time we get to final payment, so we always buy immediately and use a private company.
We almost recently cancelled 18 people due to a cancer re-occurence, but we got the go ahead from the oncologist last week, so we don't need to. Having the insurance removed a huge burden when we were making decisions.