This is basically implemented in Locale 1.0. Locale 1.0 intelligently schedules situation updates. If a situation contains both a location and time condition, then Locale won’t schedule a wakeup until the time condition is met. Once the time condition is met, then location will be checked periodically.

You might still see Location is being checked rarely even while the Time condition isn’t met, as Locale may do a full refresh every once in a while. (For example, when launching the Locale UI, and sometimes when waking the screen, or during the transition between other situations.)