Depends how fast is fast lor. When it was fast, it was still a habit that we were used to. Now it's slow, but instead of taking subjective perception, let's have some numbers!
The Sony E/FE Mount Thread:
v5 Aug 13 2013 - May 19 2014 - 279 days
v4 Nov 8 2012 - Aug 12 2013 - 277 days
v3 Jan 25 2012 - Aug 2013 - 201 days
v2 Jun 25 2011 - Dec 28 2011 - 186 days
v1 Oct 1 2010 - Jun 21 2011 - 263 days
The Sony Alpha Thread:
v59 Dec 24 2012 - Feb 11 2014 - 414 days
v58 Jul 16 2012 - Dec 20 2012 - 157 days
v57 Mar 15 2012 - Jul 13 2012 - 120 days
v56 Dec 22 2011 - Mar 14 2012 - 83 days
v55 Oct 31 2011 - Dec 21 2011 - 51 days
v54 Sep 3 2011 - Oct 31 2011 - 58 days
v53 Jun 11 2011 - Sep 3 2011 - 84 days
v52 Apr 3 2011 - Jun 10 2011 - 68 days
v51 Feb 28 2011 - Apr 2 2011 - 33 days
v50 Jan 25 2011 - Feb 28 2011 - 34 days
v40 May 8 2010 - May 25 2010 - 14 days
v30 Aug 17 2009 - Sep 9 2009 - 23 days
v20 Jan 23 2009 - Feb 13 2009 - 21 days
v10 Jul 11 2008 - Jul 26 2008 - 15 days
v2 Feb 27 2008 - Mar 19 2008 - 21 days
v1 Jun 15 2007 - Feb 27 2008 - 257 days
The start date is of the first post while the end date is found by adding
/+2500 to the end of the URL, and looking at the date of post #2501.
Date difference using this:
http://www.timeanddate.com/date/durationresult.htmlHow many days will it take to hit 2500 with a merged thread? E/FE-mount v5 went at 8.96 posts/day while Sony Alpha v59 went at 6.04 posts/day. This adds up to 15 posts/day, and 2500posts / 15posts/day = 166.66 days. Quite manageable.