Question: I was curious if the half life of Gold is 186 Days, then why does it 'Last forever' ... Wouldn't the ancient Egyptian gold artifacts be decayed to lighter elements by now like platinum? I know gold was able to withstand corrosion very well, but the relatively short half-life is kinda throwing off my understanding of why it 'last forever'.

Answer: 
Gold has only one stable isotope, $\ce{^197Au}$, which has $100\%$ natural abundance, thus considered to be one of monoisotopic elements (one of 26 chemical elements which have only a single stable isotope). As a matter of facts, it is now considered to be the heaviest monoisotopic element. For more info, read [Isotopes of gold](https://en.wikipedia.org/wiki/Isotopes_of_gold).

Aside $\ce{^197Au}$, there are 36 unstable isotopes of gold been known ranging from $\ce{^169Au}$ to $\ce{^205Au}$. All of these are radioisotopes (radioactive nuclides). The $\ce{^195Au}$ isotope is the most stable amongst unstable isopopes, with a half-life ($t\_{1/2}$) of $\pu{186 d}$. The heaviest, $\ce{^205Au}$, has $t\_{1/2}$ of $\pu{31 s}$ ([ref](http://periodictable.com/Isotopes/079.205/index.p.full.html)).
Gold has a [number of isotopes](https://en.wikipedia.org/wiki/Isotopes_of_gold). $\ce{^{197}Au}$ is stable and is the only isotope which is. So all the gold that is mined is $\ce{^{197}Au}$.