Has anyone found the output at these large context windows usable at all? IME the quality of all models goes down considerably after just a few thousand tokens

Has anyone found the output at these large context windows usable at all? IME the quality of all models goes down considerably after just a few thousand tokens. The chances of hallucinating, mixing up prompts, forgetting previous prompts, etc., are much more likely as context size increases. I couldn't imagine a context of 1M tokens, let alone 10M, being usable at all. Not to mention that any query is going to come to a crawl just to move that amount of data around (which still annoyingly happens on every query...). So usually at around 10K tokens I ask it to summarize what was discussed, or I manually trim down the current state, and start a new fresh chat from there. I've found this to work much better than wasting my time fighting bad output. This is also cheaper if you're on a metered plan (OpenRouter, etc.).