i would say that whether i speek in sentences depends on where i happen to be.
for example
at home we have our own little sub-language. sometimes complete words are not even necessary.
some times one of my biggest downfalls in a work or school setting is my tendency to fall back on such. i may begin a sentence and mid way through, i assume that my listener can infer the rest, which is not always so. i may start a sentence... 'this watch is water resistent to 100 m. so you don't have to worry about...' at which point my customer thinks 'worry about what? spilling soda? showering? scuba diving?' when infact i could have listed any of those things to accurately finish my sentence.
finishing sentences is something i make a conscience effort to do. but something i neglect because i forget that people don't know me as well as my husband or brother might.
