Sometimes I download/clone all I need, then go offline. I'm always amazed by how good it feels to go offline!
When you say you "download/clone", are you talking about just the docs, or do you actually clone the API locally?
For example, create a local, mock Twitter OAuth API so that you can program against the Twitter API without being online.
I'm genuinely curious. I like the idea of going offline, but it seems like it's not worth the effort if you're working on applications that are codependent on network APIs.
I wrote this to help: https://github.com/bradjasper/focus
For instance my work last week relies on an API that requires a VPN connection AND a windows machine.
I tested and mocked the API on windows, and now work offline, without the VPN nor Windows.