I think it is part of the configuration, the internet synchronization is only available if your sql server and windows server are enterprise versions.
The problem with performing the merge at the end of the night versus having the merge operations occur on a regular basis, is that you are running a higher probability that two changes to the same record was made and would need to be reconciled when the merge process occurs.
i.e. someone at the branch office made a change to account number 10245465.
Someone at the main office made a change to account number 10245465 as well.
Depending on how you define/setup the conflict resolution logic, the changes made at the branch might be discarded in favor of the changes made at the main office.
http://www.replicationanswers.com/Merge.aspThe other issue is that you would have to transfer a large set of data at one time.
I.e. every 15-30 minutes you may need to transfer 300K of data each way to reflect the active changes. If you wait till the end of business or at night, you may end up having to transfer 2-3GB of data which would need to be processed.