On the bitcoin wiki its says:
Transactions need to have a priority above 57,600,000 to avoid the enforced limit (as of client version 0.3.21). This threshold is written in the code as COIN * 144 / 250, suggesting that the threshold represents a one day old, 1 btc coin (144 is the expected number of blocks per day) and a transaction size of 250 bytes.
Meaning 1 BTC need 1 Day to become medium priority and will need no fees. On testnet I collected a few coins and checked the priority in bitcoin-qt client. It grows from low to low-medium to medium. Then it stops. While now on 570 confirmations it should be way higher than medium priority. Checking the bitcoin-qt sourceode there are more priorities deposited.
Did I missed something?