Yes we do. With 16 accounts at level 100, we get ~90k decay every day. However, renown continues to accrue beyond 50 million. Since our "natural" renown gain is ~150-200k per day, it effectively means we never have to worry about decay. Soon enough the buffer will be so large, even if we all took a long vacation at the same time we should not decay back to 99.
That would be Vanshillar. He should be ashamed of himself. (It's an Epic Marilith Chain btw.)