At trials, I ALWAYS run her on leash because she is consistently faster and more accurate.  However, as I have been practicing with her off leash more, I notice that she gets more tired,  and that she has gained confidence when searching independently from me.   Also, it has been really educational to see how she works odor unimpeded by me.  She usually searches really wide to round up scent cones, she ranges wider than I probably would let her.  In this video, the scents cones were fairly close to source as this was late and the temperature was cool.  But watch how she really needs space to source the 4rth hide (1:00 till 1:35)  

I have been going to places where I can let her run free (this is Elings Park, we are members here), and letting her just run around and hunt lizards for about 30 min till she is good and tired.  Then I have her wait while I place some hides and finally let her run them.  As soon as she has found them, she runs free again.  This has been working pretty well and is fun and low stress for both of us.

If you have only been searching your dog off leash in the house, I recommend taking it on the road (obviously make sure that the environment is safe).