Brecht contributed this feature to Tweak New Twitter [1] if you want to turn your timeline off and have to intentionally turn it on again, so you can't casually browse it - it's in the Experiments section at the bottom of the extension's options.
(At the time of writing I'm still waiting for addons.mozilla.org to approve a new version which fixes issues caused by a markup change Twitter made yesterday, so in the Firefox version you can't currently see the separate timeline Tweak New Twitter moves Retweets into by default)
The reason I've posted this link was, I'm using this feature myself and decided to look into its background. The minute I saw it I knew I'm not the only one who has this Twitter addiction :-)
Somewhat related: if you, like me, are battling with this social media addiction, Backlash against the Predatory Smartphone and Social Media might also be an interesting read.
(At the time of writing I'm still waiting for addons.mozilla.org to approve a new version which fixes issues caused by a markup change Twitter made yesterday, so in the Firefox version you can't currently see the separate timeline Tweak New Twitter moves Retweets into by default)
[1] https://github.com/insin/tweak-new-twitter#tweak-new-twitter