Yeah-- many people consider them 'just a fish', but you are right in assuming that they do have a central nervous system and therefore can feel pain and need to be treated with compassion.
You are also correct in the assumption that 1.5 years is a short life... it is not uncommon for bettas to reach 7 years of age when cared for properly. Why not review your betta care regime here :http://www.tropicalfishkeeping.com/b...are-faq-20058/
before purchasing your next betta?
Sorry for your loss, and welcome to the fish forum!