We have a 24 hour per day
local news channel, but it is available only on cable. So clearly the need for local news, when you want it, is there. So if you're an
OTA-only consumer, and have that need, that's prompting local channels to try to serve that need. One way would be for them to use their sub-channels for this. However, there is a religious dispute about the use of sub-channels (for example, CBS O&Os won't), and even when there are sub-channels, the question is whether the news should be on the secondary channel instead of the primary channel. Surely, you wouldn't expect "excessive" news broadcasts to bump original, first run programming, but in the battle between syndicated reruns and live news, I think live news wins.
So I could see local news before the network news in the morning (let's say 6AM-7AM), then right after the network news (9AM-10AM), then at the lunch hour (12PM-1PM), after the soaps (4:30PM-5PM), dinnertime (5PM-7PM), and after prime time (11PM-11:30PM).
So I think six hours of live local news per day is about right. And then many an additional hour overnight to rebroadcast the late local news.
