This conversation has been merged. Please reference the main conversation: Photoshop: Mirror Paint/Symmetric/Seamless Tile Paint Function
There should be an option (probably just an addition to the existing mirrored painting feature, where if the brush passes through one side of the canvas, it emerges from the opposite side, thus creating an instantly tiled image that can be modified in real time.
The only current workaround is to keep using the offset tool which is especially un-helpful for images that need to lock into one another.
Several free painting applications have this feature and it's been around for at least 5 or 6 years now in Corel Painter. Just don't see why Photoshop can't get around to this, especially since they went through the trouble of adding the mirrored painting feature.