Others may have a different experience, however, generally from the time disembarkation begins (which can vary on arrival times, immigration issues etc.) until the last passenger is off is usually no more than an hour . Given a 9 am disembarkation time, last pasengers are off by 10 am. New passengers are boarding often by noon. If you think you really have that much time, consider a post disembarkation excursion.
Disembarkation is depressing and the sight alone makes me want to laugh and cry. You go from "royal" treatment one night all dressed up for dinner to sitting like a herd of cattle in the lounge, in the lobby, on the stairs, with your damp hair and carrying pajamas and underwear in a bag.
You can't stay in your cabin and anywhere you're free to roam will be filled with more cattle. There is no entertainment and rarely is there a great spread of food too.
As much as I hate the cruise to end, I dread not having my number/color called early and having to see and experience the whole scene. I think I would prefer to get off quickly and painlessly.
While you can't stay on the ship until lunch the disembarkation process is not as grim as some people report. Our first cruise was the only cruise that we felt like a herd of cattle. After that we learned to take our book with us and sit in a lounge or, better yet, by the pool. We actually are happy when we are not one of the first off of the ship. It gives us time to reflect on our week and enjoy it just a little bit longer. There is no reason that anyone must wait like a herd of cattle. The staff asked that passengers not wait on the stairs; my hair has never been wet when I'm getting off of the ship; and I have always had a nice breakfast prior to departing the ship. We have also booked a post cruise tour when we had a late flight. It really does give you something to do instead of sitting a the airport.
Enjoy your cruise.