HTTP Strict Transport Security (HSTS) is an opt-in security enhancement that is specified by a web application through the use of a special response header. Once a supported browser receives this header that browser will prevent any communications from being sent over HTTP to the specified domain and will instead send all communications over HTTPS. It also prevents HTTPS click through prompts on browsers.
How to achieve apache with a bullet proof SSL config and HTTP Strict Transport Security (HSTS) with long duration
Here is goes

<IfModule mod_headers.c>
    Header always set Strict-Transport-Security "max-age=15553000; includeSubDomains"
</IfModule>
SSLUseStapling on
SSLSessionCache shmcb:/opt/apache2/logs/ssl_gcache_data(512000)
SSLStaplingCache shmcb:/opt/apache2/logs/ssl_stapling_data(512000)
SSLOptions +StrictRequire +StdEnvVars -ExportCertData
SSLProtocol -all +TLSv1 +TLSv1.1 +TLSv1.2
SSLCompression Off
SSLHonorCipherOrder On
SSLCipherSuite ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:!LOW:!MD5:!aNULL:!eNULL:!3DES:!EXP:!PSK:!SRP:!DSS

This gives a A+ at Qualys SSL Labs SSL Test.