Learn to keep stroking
So you wanted to see these? You know it will get harder with visual stimulation, but you have to learn that too. I want you to get hard again, apply lube and keep stroking in stanby speed.
Now start stroking faster, and faster, until you are at one stroke per second. Stay on that speed for at least a second longer than before. Start counting!
NO slowing down, NO stopping, and certainly NO cumming. This is a test, you can either do it, or fail. Get a hold of yourself and concentrate on stroking and not getting to aroused. Keep your mind focused!
If you cummed, then clean up your mess (yes with your tongue) and get out of here, you know what's waiting for you. I'm gonna call your Mistress.
If you stopped, didn't you learn anything today? If you are not willing to learn i can't help you, get out and report to your Mistress that you have failed.
If you slowed down, I'm disappointed. You had some time to rest, you should have been able to keep going longer, but at least you didn't stop stroking. Stop now, and slap your balls until you are flaccid, then do this test again, until you get it right.
If you did manage to stroke longer than before, you may slow down and ...