Well, TNG had them for every - single - act break. They were annoying. Network shows generally had them at the halfway point ("We will continue following station identification"), then one coming back in from the break. Also you'd get a logog following the opening credits ("brought to you by") and one at the end - two if they did one before previews. They were a real staple of pre-80's TV. I really wish classic shows would keep them on DVD, at the very least in seamless branching. Including things like "In Color!" and so on. The Twilight Zone DVDs are perfect and really capture the feel of the era. They even have quick promos for shows which had run on CBS at that point between the ened theme and the Production Company billboard. Great stuff.