Once you add a periodic resync you have moved the true synchronization away from the online "(eventually consistent) synchronization" and into the batch resync.

Once you add a periodic resync you have moved the true synchronization away from the online "(eventually consistent) synchronization" and into the batch resync. At that point the online synchronization is just a performance optimization on top of the batch resync. I've been in that situation a lot, and I'd always carefully consider if you even need the online synchronization at that point. It's pretty rarely required.