My first EcoSphere was the little one, and the shrimp lasted a year or two.
My large sphere has been going for at least 4 years. From what I remember reading the algae will go on basically indefinitely once the shrimp died, but my little shrimp are still kicking. I've got two little shrimp in there right now, and I've seen so much.
When the shrimp die, they go away (eaten by bacteria) quite quickly. You can see the other shrimp poke at the corpses, I assume eating some of the bacteria or algae.
The shrimp also change colors. Depending on how stressed they are and a few other things they can be quite light pink (fading into white) or bright red.
My shrimp have bread at least one. I saw the little bits in the water and thought it was some sort of debris but I noticed that it was moving. They looked like little fry. I don't think any survived (I assume died or eaten), but maybe the shrimp I have are second generation or more. No real way to know.
I haven't touched it in years. It gets a dusting every few months, but there isn't much dust so it doesn't matter. I haven't done a 'cleaning' (uses a magnet sealed inside to scrap algae off the glass) in years. It sits in my apartment that I try to keep about 70 but has been as low as 60 and over 80. They seem quite resilient.
It's a very neat desk accessory. At this point there is quite a bit of algae built up in mine so it looks dirty, and a few people have asked me why I don't clean it (doesn't help since the algae is still trapped in there) or just throw it away because it looks disgusting.
But with the two shrimp living in there, I can't throw it out. They're still happy.