Thanks for posting this great information! For informational purposes I own a Garmin Nuvi 760 and the Navteq TMC confirmed works lifetime. Total Traffic Network (TTN) confirmed will expire within a minute even though key appears valid. I will continue to search around and find a way to get TTN to work and report back my findings. If anybody has a suggestion here I'll try it and get back to ASAP!
Edit: So far I have had no success... I currently have CN North America NT 2011.20 map installed even though it's technically not relevant. On another note, for more technical information, the GTM 20 firmware is up to date a 5.50 and my actual gps software version is 4.90 (May be outdated)