Goldrun,
It is early in your diabetic adventure so you have MUCH to experience!!
A condition exists as you age called "Hypoglycemia Unawareness" -it basically means that all those 'normal' hypo symptoms (hunger; feeling light headed or foggy; sweating, palpitations, etc.) start to disappear due to appropriate hormones not being available or working.
The symptoms do change, in some cases vanish; but there are still indicators. You need to be able to recognize the 'new symptoms'. (One of my new symptoms is feeling dead-dog tired). In ALL cases, my "fall-down-lose-conciousness" hypos were NOT due to a lack of symptom, but due to a failure to acknoledge this 'odd feeling' AND CHECK MY BG with my METER.
Your BG never lies! Your meter rarely lies. Always check.
Timeframe from self-sufficient to barely functioning to danger zone? Depends; as hypo-unawareness progresses, I am sure that time frame is expanded. I usually have 120 minutes to take action, and still be "self-sufficient"