Normally Creative Suites are sold with licenses and software intended for only one platform, either Mac or Windows. There should be something on the box that indicates which version it is. If there ever is a scenario where they sold a version that was good for both platforms this is the first I have heard of it - but who knows? You might be able to tell if you read thru the files on the disc to see if there is some obvious division that identifies Mac versus Windows files being on it.
Assuming it is only good for one platform, you would have to buy another license/disc if you want to use it on both platforms.
CS6 is likely the last version to be sold as a licensed version. If you expect it to last the rest of your life, it's a nice thought but unfortunately not realistic unless you plan to have the same computer for that amount of time and don't foresee ever having to install it again some years down the road when there is no longer a server to support doing that. Eventually the software will be too old for any new hardware and that could be as little as a decade away.
The Cloud does allow for dual platform use with the same subscription.