its not issues with reflection you should worry about, the more cubemaps you have, the larger your map's filesize will be. So you should really only put them in contrasting areas, if you have a whole load of rooms that all have the same look and are close, just use one cubemap for them all.
Having one per light is probably way, way too many.
On that note, does it matter how high off the ground cubemaps are? I seem to remember someone telling me to put them at 64 - head hight.
Seriously? I never noticed that.Should be 64, otherwise the textures in the cubemap are stretched