Sample script to set it to 4 times a day for every OAB ( use caution as this could cause undue load on the server\client).EMC –> Organization Configuration –> Mail Box –> Offline address Book –> Properties of OAB –> Click Customize next to Update schedule –> modify to fit your needs (be careful to not make it often).Increase the OAB generation schedule (default is once a day 5:00 am).Outlook download of OAB ( 24 hours from last download).OAB replicated to the CAS (can take up to 8 hours).Offline address book generation (every 24 hrs).GAL generation (should happen at time of user creation but may be delayed by DC replication).
Add these all together and you can have quite a lag in seeing new users in your GAL.