Intriguing idea. I'd be a little worried about reliability of using the cell network for all my internet instead of a direct connection. Could be a nice backup option though.
Also, no this wouldn't be for life. You're relying on Ukama continuing to exist and not deciding to start charging for access sometime in the future. And even if that all works out eventually 4G will be deprecated (3G is already going away for the most part this year in the US) and then you would need new hardware.