Overnight should be more than fine, and if you're pressed for time a couple of hours, although it probably depends on your local temperature and humidity. I live in Southern California where it's warm and dry, so I find that my paints seem to cure more quickly that what contributors from cooler and wetter parts of the country typically report.
By way of example, several years ago during a 24-hour Group Build, I not only built the model, but applied a three color camo, gloss coat, decals, and flat coat. At that time I was using Dullcoat as well as Testor's corresponding glosscoat. I don't remember the timeline exactly, but as I recall, I let the paint "cure" while I grabbed a quick lunch before spraying the glosscoat. I had no problems with any of it.
Andy