If you do not update and you use Firefox, you will very likely lose Internet access on November 14, 2017.
Plus, you should want bug fixes, enhancements, and stuff.
See also Firefox 57 for more details.
Modern browsers (Firefox and Chrome) automatically update. Chrome in particular makes it very difficult to avoid such updates.
Because browsers change with every update, Pluckeye must also stay up to date. For example, when Firefox 57 deploys on November 14, 2017, all legacy extensions will stop working, including Pluckeye's. While this won't make a computer explode, it will also make updating Pluckeye much more awkward. And the Pluckeye team will then bear the support burden of helping all the those who ignored the recommendation to update.
I hope to implement automatic updates for Pluckeye eventually. But it takes time to do, and there are many competing demands (such as Firefox 57 itself!).
Fortunately, updating Pluckeye is easy. Just download it and install right on top of your existing Pluckeye installation.