Even when we've just started the walk and she's getting a treat every time she still occasionally decides against it if there is a scent that has brought down the red mist.
Those are the only times she doesn't respond so I'm not too worried. It's probably much higher than 80% to be honest.
Last night we had her responding in turns (we both have a whistle) over a distance of abut 200m without any diversions along the way despite the many scents and the number of dogs in all directions.
When she doesn't get a treat she gets a huge fuss made of her instead, and I have a special noise I only make for her when I'm really heaping on the praise. It works even when she's slipped out of the room with a slipper, a shoe, the TV remote control or a sweetie wrapper that she's pinched and knows she shouldn't have. It's actually quite funny to watch her uncontrollable desire for the attention override the mischievous nature to keep the "naughty" toy.
Wherever we go we are always complimented on how quickly she responds and well behaved and obedient she is. We think she's not coming along very quickly but then we meet people with well behaved dogs who can't believe what she can do at 7 months old. We're really somewhere between advanced and adequate. Given the time we've been able to dedicate to her training, she's doing very well and learns little tricks very quickly. We have a very good bond so once I'm more mobile we should be able to forge ahead with few problems.
Of course, she's heading towards the potential phase of forgetting everything...