Re: what is the hardest element to make and how long does it last?

What you are referring to are artificial radioactive isotopes.

An isotope is an atom with a different number of neutrons from normal (actually the normal one is also an isotope - the most common). A radioactive isotope is one which is unstable and decays naturally. When an atom decays it becomes a different element.

The time it takes for half of a sample to decay is called the half-life. This is the time you are referring to in your question.

There are over 1600 different nuclides (isotopes of all the elements), only 238 of which are stable, and only another 69 occur naturally. The rest are artificial- made in nuclear reactors. No element with a mass number of 84 or above has any stable isotopes. Some (e.g. Uranium ) have such a long half-life that they are found in nature. Others (e.g. Radon) are only found as intermediates in a chain of decay. Still others (e.g. Technetium) have such a short half-life that there are no detectable quantities in nature, they are only found in nuclear reactors.

A look through my data book revealed that there are 30 isotopes with half-lives greater than 10¹³ years, meaning 1 followed by 13 zeros, or 10 million million.
The following long half lives might be of interest:

According to New Scientist, Mar 2,1996 p 7. The subject line tells the tale. According to the article, physicists have created one atom of element 112. It lasted 0.3 milliseconds. They hope to be able to create element 114 soon, which "they hope will have a half-life of more than a few seconds".