Comment 2 for bug 1856876

To quote:

"The amount of time that a token should remain valid (in seconds). Drastically
reducing this value may break "long-running" operations that involve multiple
services to coordinate together, and will force users to authenticate with
keystone more frequently. Drastically increasing this value will increase the
number of tokens that will be simultaneously valid. Keystone tokens are also
bearer tokens, so a shorter duration will also reduce the potential security
impact of a compromised token."