Since DNN is dynamic and database driven, I think your question could more be answered by the systems you plan to put it on.  I personally have never done a site over 400 pages.  However rationaly DNN should be able to handle as many pages as you can load, with the caveate that your servers are able to handle the requests.  I know that some places use a seperate database server to support the webserver running DNN, which has it's obvious advantages.  But before this becomes a full blown ramble.  Personally I would see no reason it would be limited by page size.  As long as your hardware is up to snuff.

Russ

One other question might be what is considered a page?  Some of my larger sites many of the "Pages"  were Articles or Documents that were handled by a seperate module.  So I would think that the term pages needs to be more defined.

Russ