Just wanted to give you a heads up. I'm not sure about what your long term usage of the products you download from technet is, but they have changed how long you can uses the keys. Once your subscription expires so does your keys.
If you are using TechNet, then why wouldn't you be renewing it every year anyway? The keys should expire when you are no longer paying for TechNet.
Just wanted to thank all the people who thought it was OK to sell/buy TechNet provided Product Keys on eBay. Those people ruined TechNet for those who actually used it and renewed it every year.