As sites age and the web advances, the desire to take an old website and make it responsive can seem very appealing. For simpler sites this might be a good hold over until budget becomes available to do a new website.
For larger sites though this can summed up with the old adages of… opening pandoras box, pulling the thread that never ends and a can of worms. Even more troublesome can be depending on how the previous developer built the website, you may have to deal with re-entering content that is now outdated in it’s mark-up.
If your site is 3+ years old and not responsive, it’s time to look at a refresh of the site to a more streamlined architecture that is not only mobile friendly but also optimized for SEO.
Need to convince your boss, or yourself of why this is the time to refresh your site with a responsive upgrade, read the advice from industry leader Moz.