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 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.