We used to keep these numbers at the 300 seconds. The more important numbers were the processing times and the connection timeouts being at 10 seconds. Users are impatient, so keeping those numbers low prevent scripts from running out of control. Same thing with php timeouts.
But the wait_timeout set too low will result in a "connection has gone away" and will cause more frustration.
Definitely changing the default from the 6 or 8 hours that it comes with to a maximum of 1 hour would be a minimal task, but as @MikeDVB said, even at 30 minutes, you should be fine.
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