Clarification about maxAge vs expiry-map based time-based cache expiration

[mathiasm74]

Why is there a whole section in the README.md describing how to use expiry-map to achieve time-based cache expiration when the much-easier-to-use maxAge option seems to work just as well?

And why is the maxAge option only mentioned in the vaguest of terms?

[sindresorhus]

The maxAge option was removed in v6: https://github.com/sindresorhus/p-memoize/releases/tag/v6.0.0