How to efficiently utilize multiple vertex buffers?

Ok, so I've had a lot of success in creating procedural planet terrain with vertex buffers. The only problem is, the planets I'm looking at are too big for the XNA HiDef profile's buffer limit. Granted, I haven't gotten into much culling yet, but I"m going to go ahead and try to nip this in the bud. I've read before that I should consider splitting up my vertex buffer regardless.

So I have. My planet uses a cubemap projection so it was logical to do one buffer per cube face (this has an added benefit of streamlining manipulation of terrain, so I like it so far). My question is, how should I give the graphics device my buffers? My roommate spoke vaguely about being able to read a new buff开发者_StackOverflow中文版er to the device while it renders the old one, or something like that. Is there a very efficient technique for quickly rendering multiple buffers? Or, what is the most efficient way, besides just iterating through them, setting them on the device, and drawing them?