Due to the limited amount of neurons in the human brain (86 billion on average), there are only a limited amount of physical states the brain can be in, even if the number is absurdly large. Assuming optimal conditions involving exponential growth of the human race, as well as advanced technology ensuring that every possible experience can be had, when will we run out of unique permutation states of the human brain? 
In other words, when will the last truly original thought be had?
It is impossible to accurately determine the end of humanity's ability to create new and unique original thoughts. Consider that the human brain is not fully understood by modern science; however, through the use of emerging technologies and research study more and more is being learned every day. The human brain is also flexible or plastic and capable of generating new neurons that form stronger connections or pathways that lead to new and original thinking.
Consider my question in the context of the Boltzmann brain thought experiment
hehe XD no