r/CodeLyoko

I've been watching the series from start to finish. Currently half way through season 2 and im wondering if I missed something. At some point they stop using the Return to the Past function cause it makes Xana stronger. However, ever since the episode where Ulrick uses it to win the lottery, they are just fine to keep using the function?? I feel like I missed one of them saying oh it's fine now. Can someone help me fill in what im missing?