Learn to keep stroking
Good boy, i know you could do it. HEY, what are you looking at? You'll get to see them, no need to hurry. Didn't i tell you to do it slowly ... you boys only seem to be slow at learning.
I want you to increase your stroking speed again, until you are at one stroke per second. Thats a nice pace to look at! I want you to count the seconds you can stay on that speedlevel of stroking, and when you feel you are getting too close, slow down until you reach standby speed again. But no stopping!
Give me another minute of standby speed stroking and then stop. Yes stop stroking. How many seconds did you manage? For each second you get one minute of rest now. Go clean yourself, get that old lube washed off, and cool your cock with cold water. You have done good so far.
When your resting time is over, come back and ...