How often do you back up the distribution database for transactional replication when sync with backup is set to true for the distribution database? I'm trying to figure out how often to back up the distribution database when "sync with backup" is set to true.  If I understand this correctly, sync with backup ensures the distribution database can retrieve all transaction from the publisher's transaction log when/if the distribution database needs to be recovered.  It does this by preventing the publisher's transaction log from truncating records until the distribution database has been backed up. 

If this is the case then in order to prevent outrageous growth in the publisher's transaction log, the distribution database needs to be backed up almost as frequently as the publisher's transaction log.

Does this make sense?  If I decide to do back up the distribution database almost as often as I back up the publisher's transaction log is there a good way to estimate the performance impact?
I back up all of my transaction logs at the same time, every two hours.  I haven't had any issues with Log growth since I set that up, and I haven't had any issues with replications because of the log backups.

I think the best thing is to watch for how fast your logs grow, and plan your log backups accordingly.  Alternatively, how fast you want to be able to restore databases will also affect how often you make backups.