Trust me, it lasts more then long enough. You'll mainly be using it for AV/EB fights. And if the fight lasted longer then 45 seconds, chances are your fighting Romulus or something. The fact I've seen it's hold go off on Elite Bosses and Archvillains through the purple triangles makes it even better.
"The danger is not that a particular class is unfit to govern. Every class is unfit to govern." Lord Acton
Madam Enigma's History
Glad you found the answer. In case you're curious City of Data has the answer but it's kinda hard to find. Basically you have to go to the page for the power that it grants rather than the main page for the power. That has the lifetime:
http://www.redtomax.com/data/powers/...as.Noxious_Gas
Thanks for the input guys. Sounds like it'll be pretty brutal on my new Demon/Poison. And thanks for pointing that out Adeon, I actually found that page and somehow missed that detail - lesson learned I guess 
How long does it last once you've cast it on a pet? I can't seem to find a duration on either Mids' or City of Data.
Edit: Nevermind, I had the brilliant idea of actually searching the forums (hurr), and I found that little tidbit. 45 seconds. Seems kind of short.