I have a number of pages i want to move to a new url by using 301's. How long do i need to keep the 301's in my .htaccess for? Is it a case that once google/yahoo/msn have followed the 301's they will ignore my old site and use the new one meaning i can remove them from my .htaccess?
I would just leave them... Someone may link to your old page 5 years down after referencing it from a website that also linked to the old page. If you remove that 301, google will follow it to a 404 or a double content page.