You didn’t tell which “solution” you are referring to. You didn’t press the “reply” button on the relevant post.
This topic is quite old, starting even before the chat API was released, and has several diversions that are not answering “remember previous messages”.
Here’s a better recent thread to move to:
The conversation length cannot increase infinitely, because the AI model has a limited context length area to supply it past conversation. Management and truncation is required. The maximum compute would actually be in producing a very long output, as the input size has a smaller effect on the processing cost.
ChatGPT has very aggressive minimization of past conversation turns, giving the AI only what is needed to understand the present topic, so an otherwise ambiguous question like “what about the other one?” can be answered.