For me its got more to do with the journey on the ground. If I'm being picked up by car and being driven to a hotel etc., then I'll happily check-in a bigger suitcase. If I know I'm going to be battling public transport, then I'll travel lighter.

Usually I will check luggage because I like to take a pen knife, "some liquids" etc., and even if not, I might want to bring something back of that ilk.

I've never lost a checked bag, only once had one delayed, and twice had suitcases damaged (though not seriously). So I never fear checking baggage. Frankly it annoys me when I have to wait so long at a gate x-ray because people ahead of me are pushing the limits so much - roll-on, separate laptop bag, plastic bags with duty free, handbags, etc. It also increases boarding time as pax block the aisles whilst trying to find somewhere to stow all this stuff.

To answer your specific point - I suppose it has little to do with length of stay, weather etc. Except that if its a very short trip (ie day trip, or one night away) then its unlikely I would check luggage. Mind you, I did a day trip to London from Saigon and managed to check 42Kg (about 92lbs)