I use WordPress and
/sample-post/ URLs for my posts and
/yyyy/mm/ for the archives.
Google has indexed the site fully.
Since the archives currently display full posts I've thought that I shouldn't let Google index the archive pages because they contain the full posts and that will be duplicate content. Thus my robots.txt contains:
Disallow: /2009/ Disallow: /2010/ Disallow: /2011/ Disallow: /2012/ Disallow: /2013/ Disallow: /2014/ Disallow: /2015/
Do you think this is good practice or would it harm my rankings and/or reachability?