The reason baking exists is for things like what you are doing. It bakes the radiosity onto the scene so you can save time. Since there are no characters to disrupt any shadows then you can get away with baking. I believe the actual manual for LW (or some documentation) says that one of the uses for baking is architectural flythroughs. The time taken to render a prebaked frame has to be shorter that the cheating method you are using... and you can just let LW do all the work for you, let it sit and render.
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