Lifespan of sand sifting starfish?

[gmdcdvm]

I was just wondering what your experience with sand sifting starfish was like? I have found mixed results doing a web search. Some say they only last months before they waste away. Other sources say they can live longer. If you have/had one how long did it live?

I ask because I have had one since I started my tank. It’s been about 4 years and today it looks like it is slowly falling apart like most starfish when they die.
Thoughts?
Gerry

 

[Kensington Reefer]

6 years so far
I know there is 1 but might be 2
I put 2 in, but don’t often see them both at the same time
Deep sand bed
66”x24” footprint