Excellent site which brings us to an obvious question: At what point should we as developers consider a site good enough? There's an infinite tail of worse and

Excellent site which brings us to an obvious question: At what point should we as developers consider a site good enough? There's an infinite tail of worse and worse speeds and latencies. At some point it makes business sense to stop optimising, and for businesses with lots of users that point is inevitably before supporting 100% of users. So how do I prove to the business where the 90th and 99th percentiles are, within some reasonably scientific measure of uncertainty? Aside: I just checked the site I'm working on. When throttling Chromium to GPRS speeds (500 ms, 50/20 kb/s) the main page has all the text on it by 16 seconds after a hard refresh.