Yes I think it would still be a good idea to require expiry date for &quot;immutable&quot; content, just as a safety net if something is misconfigured somewhere etc - then when you fix a bug, you will know the precise time at which it will be gone for everyone (hopefully the expiry date was not set to 10 years).<p>However I wonder what is the typical cache lifetime of resources on current web. IIRC someone on HN posted like a week ago that from their study, it&#x27;s rather short - stuff is evicted from cache quite rapidly if not used. So fast that getting a cache hit for jquery from CDN is quite unlikely very often.