I'm pondering moving an old blog from Movable Type to WordPress soon.
The old MT posts all have URLs like http://www.mysite.com/001416.html. Clearly I can't keep the same URLs with WP since WP uses php. So once I switch, I'll have about 4000 old posts with new URLs in the now-standard mysite.com/2003/06/title-with-keywords format.
I know how to redirect a URL with htaccess.
But here is my question: how many redirects can you safely have in one htaccess file? Would 4000 separate redirects slow down the site? Or have any other negative impact?