Good day. What makes them effective is having something specific to communicate rather than simply moving a camera around impressively. If the relationship to context and changing light is the story, that's a legitimate brief.
Architectual animation handles time-of-day transitions well, which stills fundamentally cannot. On length, ninety seconds is roughly the ceiling for web and investor use, and shorter usually performs better. Costly caveat: every second of animation multiplies render time, so a five-minute piece is dramatically more expensive than two minutes, not slightly. Storyboard first and cut ruthlessly before anything gets rendered - changes after that point hurt.
