I do my own color and b/w processing for my studio photography, as well as my personal photography. I have let exposed Ektachrome sit in a holder for a week in the studio, while I shot enough holders to make up a "run" and I have not experienced ANY deterioration of image quality.
Originally Posted by razzledog
In some rare instances, I have gone as long as a month between exposure and development of E-6 Ektachrome 4x5, with the film remaining in the film holder. No problems. B/W would have even better keeping qualities.