What I'm saying is ive done deep digs and yes the dogs stayed there steady away then the last two foot the pressures on . The dogs come out with not much on him . Then I've done digs say 4 foot that's been pressure from start to finish . The dogs had to work twice as hard in the small dig than the big dig . And it's also happened vice versa . So I don't think you can go on time or depth . I think it's how long the pressures on test a dog . This is just my opinion .