Since 12.2 has been released, I have see this ETCC patch checker be updated about monthly, and sometimes twice a month. I recommend downloading the new version anytime you want to update AD/TXK patches.
We release a new ETCC bundle approximately 2 to 3 weeks after the CPU/PSU 's are released. This is quarterly, so Jan - Apr - Jul - Oct. You can follow Steven Chan's blog to see when we release them.
This is the latest.