How long does nicotine stay in your system?

Could you please elaborate on the duration nicotine stays in one's system? Does it vary based on factors such as age, weight, and frequency of use? Are there any reliable methods to expedite its elimination from the body? Additionally, how does nicotine's lingering presence affect an individual's health, particularly in the long term? Lastly, are there any tests available to accurately measure nicotine levels in the body?