Depends what you're going out to do and how much of home/access to work you can leave behind. Camera and gopro kit, laptop, mobile, ecig kit, essential clothes for if your case gets delayed ... some airlines say max 5kg carry-on. Mine's never less than about 10 with all that which can't go in the hold !
Suitcase full of diving stuff and seeing as going to wind up paying may as well shove in maps, proper towel, spare rucksack for walks or bike and fill it up with clothes in case you wind up going somewhere especially "nice" (which never happens in my case
). Throw in some sci-mx and a shaker for emergencies and on a very short trip some snacks etc. too saves wasting time shopping. There's 20kg without even trying
BUT - you can hit the ground running every time for pretty much anything. So sod it I always pay to check a bag in
.. and feel completely self-sufficient from the arrivals hall (if it shows up !)