Buffer : This is definitely too long.
My only suggestion : disable OPEN GL and use smooth and flat shaded preview for only one of the views (i.e. main camera) and "wireframe" for all the others. You will get a fast refreshing rate. You could also hide some layers to improve it.

Well Guitta, it seems that VUE acts strangely with some imported meshes. On one scene I went up to 40 millions polygons without any problems (1GHz PIII-256Mb). But It was only made of "VUE stuff" : primitives, terrains and vegetation. While for another scene I used a DE ESPONA 3DS model of only 400 000 polygons and VUE was getting really slow. Strange... Maybe Steve can answer this ? Could you ask him Guitta ?

Eric