I will always send my full call sign.
This is point #6 in the DX Code of Conduct: http://dx-code.org/
Operators in the DX end of the pile up simple don’t like partials call at all. It only slows them down, preventing them from working more stations.
Be it in a contest or in a DXpedition, as in life in general, time is the most precious thing and you cannot recover it once spent!
Some operators will simply not come back to stations sending partial calls, they may eventually write them down until the calling op transmits his/her full call and then make the QSO. Otherwise the partial call will only make it into a post it or note pad, but never in the log!