octopus tank upgrade

What kind of requirments equipment wise do they have? I would love to have one but more interested in the knowledge of why they die so quickly

 

Just regular reef equipment.
If you google "octopus aquarium" the first 2 results are quite good, as they give the most important information on keeping them.
As for the age limit, I honestly don't know. I personally think it's due to lack of activity.
Also, the male often dies right after the female has given birth and the female often dies after the little octopusses are a little bigger.
If you prevent them from breeding they can get a little older, but indeed, mostly not more than 2 years.
They have been known to get over 10 years in age though, even in captivity (look at Paul the Octopus, the Soccer WCS soothsayer).