I only got like 10 months out of mine but smaller 80g tank. you would be better to get a nice group of those big tongan nacarius snails. Those have lasted well over a year cleaning the sand.
I currently have one going on 3 years. I don't see him often but I just saw him last week so I know he's still going strong somehow. I started with 2 though and I'm going to hazard a guess that the other one is gone. Unless I happen to see 2 at the same time that belief won't change. Last time I saw both of them at the same time was 2 years ago for reference.
Unless they have a large established sandbed, they just starve.
My 80G cube is no where near enough sandbed for them. Something in the range of 150 or larger, and well established before adding, they would probably be fine long term.