If google can not SEE the content, the content is not there; they will remove it from their index.
As for the 40k limit, where is this coming in to play? It doesn't make sense that they'd have a 40k limit when their sitemap index allows up to 50k links per sitemap...
The 40.000 files are a limit that I read some where in a SEO web site. It was a while a go and I had it on my mind.
Now I'm running a sitemap program and then it came to my mind again.
This is why I decided to reduce the size of my forum, just to have a 'fresh' topics on google, but if one user want, he/she can go back many years.
Per the first part of your response: I could not get it.
I want to move part of my forum to a folder that will be behind a "robots.txt" file that will not allow google to see it, but normal users would be able to search it.
I'm not sure how could I split the forum in that way: old posts on a specific folder, new posts on the regular folder.
