Indeed. I've seen DBMSes take close to 10 minutes to gracefully exit, even when idle.

Timeout in sysvinit and service files, for a graceful exit, is typically 900 seconds.

Most modern DBMS daemons will recover if SIGKILL, most of the time, especially if you're using transactions. But startup will then be lagged, as it churns through and resolves on startup.

(unless you've modified the code to short cut things, hello booking.com "we're smarter than you" in 2015 at least, if not today)

Yeah, as I've said on many incident calls...we can pay for transaction recovery at shutdown or we can pay for it at startup, but it's got to happen somewhere.

The "SIGKILL or keep waiting?" decision comes down to whether you believe the DBMS is actually making progress towards shutdown. Proving that the shutdown is progressing can be difficult, depending on the situation.