[whpalmer4]

By default, OmniFocus attempts to sync 1 minute after any change is made, and hourly thereafter. I think all versions of OmniFocus attempt to sync when they are launched, and OmniFocus for Mac also syncs when asked to quit.

Note that the clients do not sync with each other directly, but with a central repository. If you make a change at t=0 on one client, it syncs the change at t=1 minute to the central repository, but another client may not see that change until it syncs, which might be immediately, or might not be for almost an hour, assuming it is running the entire time. It's generally a good practice to sync a client both when you start and finish using it. This ensures that you're looking at all the latest data, and that your changes are immediately propagated somewhere else. Less chance of lost data if something happens to the device, less chance of duplicating or losing a change due to editing the same action twice, and improved sync performance.