unless you're fine with possibly releasing disease into your huge tank and kiling everything... sure!
i only don't QT mine because i always get them from the same place, a place i trust, and everything in my tank is from them, but if i were ever to get a larger tank i'd qt without question.
it's a safety blanket so you don't lose all your investments, and wonderful pets! and its not like its expensive, a smaller tank with some simple filtration. unless your one of those people who treats even if they see nothing wrong, it's all just observation for about 2 weeks, and to make sure they eat.
and remember, nothing good in saltwater happens fast.