I recently wrote several novels using Gemini 2.5 Flash and the context rot is noticable but happens far later than what this report implies. In my experience, 50K to 100K tokens were required for it to start to disregard the initial context (e.g. the output language). Maybe a complex task like creative writing makes the impact harder to measure or observe; in any case it remained okay enough for me, once I supplied missing contexts from time to time.
If you are interested, one of the novels is in fact open to the public: https://w.mearie.org/maidens/. But it's written in Korean and no English version is available yet.
