[j-nsp] Radius Interim-Update load

[Gabriel]

We have an ERX310 router with over 10,000 sessions of ADSL customers and
would like to enable Interim-Updates through radius to have it send
updates every x minute to update accounting....my concern is that this
may add a LOT of load on the radius accounting server. Does anyone know
what would be a good interval for these updates or maybe give me
pointers?