Rated 5 out of 5 stars

Fantastic little addon!! .... Is there somewhere I can download it and save it to my PC in case Firefox outdates it lol

This review is for a previous version of the add-on (3.3). 

LOL. The "stable" version of this addon is, and will remain, here at addons.mozilla.org. Now that Firefox, Thunderbird and SeaMonkey are equipped with a "default to compatible" feature, it is expected that NTT won't become "outdated" by any foreseeable future version of theirs, though new NTT versions will of course be uploaded to fix bugs and/or add features.

The development source is on github (see the link on the "addon home page"), you will normally not need it unless you want to add features and/or help fixing bugs.