martinibuster - 9:12 am on Mar 18, 2010 (gmt 0)
phranque is correct. Re-read the original post. The OP states they changed the Robots.txt to the version that allows bots to access the site after they initially displayed the wrong version. But that's not what is under discussion, despite what the title of this discussion shows, which is the source of the confusion. Here is what the discussion is about:
So my question is that how long will the Search Engines take time to acquainted of my changed robots.txt?
This is why it's important to accurately describe what the discussion is about. ;)
As for the answer, keep building links. Bots revisit a site according to how many links you have and how worth crawling they are. Robots.txt will not slow down how often a bot visitors your site. So once a bot follows a link to find your site they will see the correct robots.txt and proceed to index your site.