Hmmm well, sounds like your getting all the advice you need. Reciprocity also occurs during extemely short exposures as well. Shooting outside for long exposures can create a colour shift regardless of the film your using. This can be corrected in the printing stage with filtration and a colour anyliser. i realize not everyone has access to one but if you have a custom lab nearby, you can let them know about the exposures and they will compensate. batch processing at most labs doesnt give proper results when deviating from the "norm". I'm a little luckier than most being able to access my lab at work and through the custom lab we use on other projects. the 160 film should be more then adaquate to do the job you want and i find its colour shift to be minimal. the more sensitive faster films tend to be more unstable in regards to colour shifts over long exposures and can cause bleeding. hope that helps.