I'm on my first saltwater tank, but I've been doing freshwater all my life; and yes, I qt. I have four tanks, two display and two quarantine, 2 fresh 2 salt. Well, I do have a 5th devoted guppy tank, and a freshwater puffer in the works, but they're in a different room. I qt in 30 gallon tanks, just because that's what I have available, and I've found that new fish adjust much better after they have full reign over a 30 gal, it seems to make them less afraid and more eager to eat. I keep them in there from 3-6 weeks depending on the species and where it came from. And personally, I'd rather have a backup tank just incase something goes wrong with my main tank.
I never take chances with anything I love, fish included.