This is really good information. Thank you!If you want him to develop more control over how fast he cums, you can work with him in that and reward him.
Start slow. If in these highly aroused settings and he's been aching for days, maybe start with double the number of seconds you think might be normal for him. If it only took 5 seconds- tell him he can't cum until at least 10 seconds. Once you get him able to hold off on ejaculations for a full minute, add one minute (or 30 seconds?) each time as the goal. Don't advance to the next goal until he's met the last one at least 3 times.
You'll want a reward system. Figure out what that is and what you think will work best for him.
You might also want a punishment system. Adding delay to when he's allowed to cum next time. Extra chores? A spanking while he's wearing his cage? Spanking can be both very erotic and very intimate while also humbling and adding a pain dynamic. It doesn't even have to hurt very much at all. If you spank him with your hand his pain and the burn on your hand are likely to be similar.
Maybe pull him over your lap and spank him the number of seconds he was short by?
Just a thought.
Just remember... when you hold the key, it gives you lots of opportunity to train him to be the good boy you both want him to be.
I have been wanting to start something like this, but to be honest, with the cage, we both get so aroused it is hard not to go straight to the orgasm. But I will start this soon. I need him to get better.
