There was an article on cropping and not throwing away as many pixels in the TPPA mag arrived just this week. Its theme was to make sure to leave the pixel field blank on the cropping tool. Hopefully, it will be online at their website soon.
www.tppa.org
That having been said, I leave the .psd uncropped until I am producing the .jpg for the lab. Then I crop, flatten and save as a new filename.psd and .jpg. Then the .jpg goes to the lab.
If you ask 10 PS-ers how many ways there are to change a lightbulb, you'l get 10 different answers (at least). Otherwise, there is more than one way to skin a cat. Some just leave you with less fur to eat than others.