Sorry, it doesn’t fail to recognize it, it just doesn’t think 45 minutes is terribly useful Anything under 24 hours will fail and if it is between 24 hours and 30 days it will still get a warning.
Been waiting for someone to raise this for a while as I’ve always been confused by this one…
Given we reckon that a good proportion of users hit our sites with a clear cache (http://www.yuiblog.com/blog/2007/01/04/performance-research-part-2/)
then surely the big win is ensuring that the browser cache kicks in for at least the duration of the browsing. Long (>30 day caching) is irrelevant for half the users. But relevant for the other half, of course.
Long is good, but the grading doesn’t fit the facts as I see them.
FWIW, the in-session cache logic for browsers is significantly different from the logic that is used when they come back in a new browser session so trying to tune the cache for their session doesn’t really buy you much.
Even in the Yahoo study, 40-60% of users (and 80% of page views) were a cached experience and the performance improvements are enormous. The main point of the post is to not ignore the first-time experience and assume that your users have everything cached, but the same is true the other way - if you could make the experience 80-90% faster for 40-60% of the users it certainly deserves your attention
Unless you’re willing to accept your site being broken for 45 minutes at a time, you need to do the same work to allow for a 45-minute expiration as you would for a long expiration so why not?
Anything under 24 hours will fail and if it is between 24 hours and 30 days it will still get a warning.