BrandBay

I acquired a Tier 3 license last year and I can say that it is a very practical tool for those who work with brands for several clients. Not only to have all the information from a client's brand book at hand, but also to be able to share this material securely with freelancers and suppliers.
I frequently use the Chrome plugin to have instant access to material from a brand I'm working on, to copy colors and download logos and fonts when creating content.
As no tool is perfect, there are still some improvements to be implemented, but I can say that they are improving the tool regularly.
And another very important thing in the case of a lifetime tool, if you need it, the support really works!