Regarding how long: it depends on length of messages. But let's say when there are around 2000 words total in the conversation. https://help.openai.com/en/arti

Regarding how long: it depends on length of messages. But let's say when there are around 2000 words total in the conversation. https://help.openai.com/en/articles/4936856-what-are-tokens-and-how-to-count-them https://help.openai.com/en/articles/4936856-what-are-tokens-... 2 cents per 1k tokens