I get it too, but this is a pretty harmless thing. Their lifespan is the same as regular zebra danios as far as I have read/heard.
My daughter does keep asking for more glofish because she really liked them too. I probably will get some the next time I have room in a tank. I just feel so sad every time I see them in the stores. It was my first fish experience, and I had no idea what I was doing. I had 10 glofish in a 5 gallon tank because that's what petsmart said to get. I very quickly lost one and then decided to research and was horrified at what I was doing to these poor creatures. I immediately went out and got a 10 gallon tank, and the remaining 9 survived a fish-in cycle in which I was literally changing 75% of the water twice a day, during which time I had also just had foot surgery so I was limping around with plastic pitchers and solo cups. It was a mess.
I then bought my 55 gallon tank on craigslist and did a proper fishless cycle, using ammonia and seeded sponges from the LFS. Got it all set up and planted with live plants. Moved the glofish over. Two days later, they were acting weird. Kind of floating mid-tank, gasping. I posted all over every forum I could think of, wondering if there was some kind of toxin in the water. I pulled out all the decorations, ended up taking the whole tank down, scrubbing it with vinegar, and refilling it. I was doing water changes every couple of days. Then one morning, I woke up to all of the glofish dead lying at the bottom of the tank. I was devastated. And my daughter saw it too (she was barely 3 at the time). Come to find out, it was lack of oxygen that killed them. I learned through a long conversation with the guy at a local store who looked at all my pictures and stuff that I hadn't arranged my canister filter output properly. I had also baffled it because the fish were having trouble swimming in the current. So no current + no surface agitation in an extremely deep corner tank meant there was almost no oxygen exchange and the fish suffocated.
I was so surprised and relieved that these poor fish had survived this brutal fish-in cycle and then I killed them. They lasted almost 2 weeks in water with almost no oxygen in it. They are tough little guys, and I will always regret that.
Anyway, I really recommend them. Sorry for the sad sob story. But it shows how hardy they are to have lived through a lot of my bungling. Now that I'm writing this I really want to get some more. I do have room for another school of fish in my 120 gallon. I was going to double the rummynose tetras, but maybe I'll get some glofish instead...
Bettas: Roland, Belle, Snow White, Polo, Elise, and Titan. | 120 gallon community tank | 55 gallon angelfish tank | 20 gallons of guppies