This is the same argument I routinely have with client id/secret and username/password for SMTP. We're not really solving any major problem here, we're just pretending it's more secure because we're calling it a secret instead of a password.

How long the Jira access lasts depends on you / Sentry detecting and solving the initial intrusion. It doesn't matter how long the Jira token itself lasts if the attackers have access to the database in which its stored or log files in which its been dumped or something like that.