May be one note to increase T3212: instead of every 4 hours, maybe do every 8 hours.
It reduces the amount of location updates in your network, reducing the SDCCH load. Yes it is true, but only during the night – nobody send/receive SMS nobody makes MTS/MOC call.
During the day/BH, is the saving of resources nearly zero. Because every make a call or SMS – The timer is restarted in the mobile, but also in NSS. If the NSS receives a LU before the expiry, then the timer is restarted.
If the timer in the NSS expired, than NSS will try to page this MS. Than the mobile becomes “IMSI DETACH”-ed.
But it depends on behaviors of your customers.