You may not know it, but your ChatGPT chat sessions have a strict limit. They can only last so long before you reach it. Confusingly, there also appear to be two types of limits. The first has to do with memory.
The memory limit (the amount of current chat that ChatGPT can remember for context) is measured not in time or the number of messages you've written, but in things called tokens.
A token has about 0.75 English words, on average, so “The cat sat on the rug,” which has six words, is equivalent to between seven and nine tokens. Long responses, large tables, code, and detailed documents can consume many more tokens than short text exchanges.
What matters is the model's context window: this is the total number of tokens it can consider at once and will vary depending on the model you are using.
The context window
OpenAI does not publicly document the context window of each model available in ChatGPT, but it is likely measured in hundreds of thousands of tokens. But if you reach it, you can expect ChatGPT to start forgetting things from the beginning of the conversation.
Of course, if ChatGPT simply forgetting things from the beginning of the conversation was all that happened, then there would be no need to be alarmed. But as one Reddit user discovered, there's another limit, which is much more serious: ChatGPT can end a chat if it gets too long.
When this happens, you simply receive a message that says, “You have reached the maximum duration for this conversation, but you can continue talking by starting a new chat.”
Even though OpenAI has not officially documented the duration of the chat, there are many reports and screenshots of this warning message, so while the evidence is anecdotal, it appears genuine and I think it is still prudent to act on it.
When you reach the limit
I have a very long chat thread that I use a lot on ChatGPT, almost every day, and I started wondering when it would reach the limit, so I asked ChatGPT if the current chat was close to the limits of its context window and it said:
“I can't see the exact token count or hard limit for this thread, so I can't tell you “you're at 78%” or anything similar. That said, based on the amount of text in this thread, I'd estimate we're well over halfway there and probably somewhere between 60% and 80%. range of what a typical long GPT-5.5 chat can comfortably contain before the previous context begins to be compressed or deleted.”
ChatGPT estimated: “If I had to put a number on it, I'd say about 70% full, give or take quite a bit because OpenAI doesn't expose the actual count.”
So, it was probably time to start thinking about opening a new chat based on the same topic.
How to prepare for a new chat
A chat thread can start to feel less like a thread of messages and more like a shared workspace that will always be there. In reality, it is still a temporary container with maximum capacity. Over time, the conversation becomes too long, the context becomes harder to maintain, and the chat reaches the end of the road.
Basically, your only option to preserve the chat is to recreate it in a new chat window. That way, the token usage is reset to zero, as is the conversation duration limit. Of course, you'll lose many of the biases or subtle influences of the previous chat content, but it's still your best option.
Because I'm getting close to the limit of my chat, but haven't reached the limit yet, I'm at the right point to do this now. The key is to do it early, before you reach your limit and it's too late to ask more questions.
To recreate the chat, simply ask ChatGPT to create a message to recreate the current chat, then copy and paste what it produces into a new chat window at a convenient time. Try this message: “Summarize everything important about this chat and create an opening message that recreates the context in a new conversation.”
Now you can start using the new chat.
If you have a ChatGPT conversation that you've been using for months, it might be worth asking the AI to summarize it now rather than later. Because when the warning message finally appears, your only real option is to start over, and by then the ability to recreate the exact chat may already be gone.
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