My hypos can often be accompanied by a bit of panic...so I over treat sometimes too! (and I have been T! for over 30 years now!) 15 to 20 minutes sounds about right to me..although it must feel like a lifetime I am sure. I am surprrised though about your son running low. They ( ie the medics) often start a diabetic on too little insulin, and then build it up to avoid this. I would seriously give them a call, becasue if he is having regular hypos, whilst not dangerous with a caring family around, does indicate that his insulin levels are wrong somewhere. This is particularly true if you are able to almost predict his hypos! Give the Dr a call, so they can help adjust his doses,
Good luck, it sounds like you are doing a great job b ythe way!