I'm just a user, but I'm pretty confident that my device will have that access for its "life" based on the promise. Remember that "life" is the life of the registered device though, and not the human user. Obviously they have to make money somewhere to cover ongoing cost of the servers, development, and support. Right now, it looks like they are doing that through increasing hardware sales and licensing it to other companies like Seagate and Buffalo. I think we can count on at least being grandfathered in for free service should they ever find the need to start charging in the future on newer devices.

I'm not sure if they technically offered free mobile apps for life, but it does help them sell hardware, so I think chances are good at this point.