I have two clowns in QT right now. I ran them through copper and some other meds. A few days after I pulled the copper out, they showed signs of either ich or velvet.
I'm not in the process of doing the hybrid tank to tank method, hopefully that'll break the cycle.
I think the clowns have been in QT for nearly 3 months now.
My DT has been ready to go and fully cycled for *months* now and it's still sits there, empty, eagerly awaiting it's first fish. I have a bunch of corals in their own QT as well.
In the past we've had threads where people ask how to get started with SW tanks and one of the things often mentioned, possibly because the BRS guys suggested it, is that the second you even start thinking about a tank, get your rock and start curing it. After all this, my suggestion is that the first thing you do is get your first few fish into QT. If they finish QT before the tank is ready, they can stay there longer. If QT lasts longer than expected, you don't end up with an empty tank for months.