Earlier quoted context omitted.
I thought maybe the author meant that they'd retain enough of the months of prep that they'd already done.
Generally, once you've practiced enough to clear most tech rounds once - it's not too difficult to do it again. If I'm going in for an interview then I might still need to spend ~1-2 weeks practicing again to do well. Earlier in my career I spent months practicing LC.
8 years ago, I spent time with CtcI, etc., and was immensely prepared to interview but, for me, that's all largely lost to the ages now.