My Beta recently passed away this winter
. I had him for about 5 years, I dont know exactly how old he was when I got him at the pet store.
He was extraordinary, as soon as I would walk near his bowl he would go nuts. He would follow my finger along his bowl and always made me smile.
Im not even sure it was age that killed him, he seemed perfectly healthy the day before he died. I had recently brought home a new kitten, claws and all. Then one day when I went to feed him I noticed he had a huge gash in his head. I dont know for sure but I think the kitten may have done it. My older cat would always sit near his bowl and dip her declawed paws in his bowl, he would swim around her paw totally un afraid. (I always shoo'd her away tho, cuz i didnt want her eating him!) I tried to save him but he died about 3 days later. I cried so hard over a fish =(, my husband thought I was silly.
So a beta can definately live a long time if you give them lots of love and proper care!
It is really important you change their water weekly if you keep them in a small glass bowl, with no bubbles or filtration. Only empty about 70% of the water, because keeping that fish bacteria is still important even for a beta. I would completely empty out his bowl about every 1.5-2 mo, and even then didnt scrub down his marbles. I would bleach everything once a year... USE lots of Stresscoat (or de-chlorinizing item) until the bleach smell is gone, and even then do it 2 more times =)! And talk to them, mine loved it