What are the consequences of a low Acct-Interim-Interval?

[Houman]

Maybe I'm overthinking it, but we have currently the interval set to 300
seconds.
What happens if I set this permanently to 15 seconds? Based on currently
logged in users (around 700 users at a time), the database, as well as the
freeradius process (CPU/Memory), will be a lot more utilised than before
due to an increased number of updates.

post-auth {
        update reply {
                Acct-Interim-Interval = 15
        }

Is there an industry standard value that is considered fair? Or can I go as
low as 15 seconds without fearing scalability issues?

Many Thanks,
Houman