1 1/2 to 2 hrs for me. Wish it was quicker, and it should be. Train with a partner who just happens to be the gym owner, so when someone needs to re-new gym membership or has a question he has to help out. Drives me a little nuts at times (even though he is a killer training partner!! Love the Pit Bull mentallity but hate the Poodles!!) Rest between sets for us is as long as it takes for one of us to complete a set.
We have lots of people asking us program advice or even ask to jump in on a session with us which takes even more time. UGGGGGHHHH!!! My avatar is what we have on the back of our gym's t-shirts told my training partner it should have said, "Do not disturb while training!!"