One other factor is experience. This was not my first event like this. It did take a fair amount of effort and time to edit. But it was a labor of love. My goal was to get it down to 15 min. So, in that sense, I failed. But my wife always wants these video memories to be longer -- not shorter. If I cut things too much, she notices. So it's too long for general audiences but, for us, on a cold winter's night, just right
Do you have any Cunard experience?
I know exactly what you mean regarding how long a big project should last. You shoot loads and loads and what do you leave in and leave out? Obviously, you don't want to bore people with too much "baby on lawn" style footage.
What I tend to do is run though all the shots to make sure that I have enough of the main things and people that will matter, even if it means recording extra footage afterwards (if possible).
I always make sure that it has a start that establishes where the venue is, then the middle with all the important parts including onlookers/audience (if it has any). The end can take many forms depending what type of video I am filming, it can end with a fade out of the outside of the venue or a dance or whatever, but I always wind it down without a sudden stop, and if it has an audience, fade out on them.
I am a bit ruthless on a lot of shots and do cut them tight in post unless they are important, this is probably left over from my old "proper film" days when it was expensive to buy.
After I have finished it, I run it on the TV in front of my wife for an honest opinion to see if it conveys what I am intending it to show to others, as it's easy for me as I was there. Very often I will alter parts before I am satisfied, and I will overdub music if it is feasible. I try and make sure that any part of the audio track is as good as I can get it and I always use a separate sound recorder. If it's a band I will (if possible) plug a flash drive into the mixing desk, but I will still use the audio recorder with mikes as I have had a few disasters in the past with the singer or some instruments not mixed properly!
Regarding Cruise Liners the answer is no, they have never appealed to me and the only sea voyages that I do these days are on the cross-channel ferries or to Nothern Spain, if I am not flying for some reason.