Coby will turn a year old this month. He is 99% trained for the rooms that he has free reign in. We gradually add rooms as the trust is gained and as we are able to give 100% attention to in those rooms. He does not have free run of the house yet. We hope to one day not have to walk over baby gates.
My philosophy is to make it as impossible as possible for them to make mistakes. That way the whole process is positive. You are right, you can't watch them like a hawk at all times. And for those times in rooms in which they are not fully trained, they need to be penned or crated to avoid mistakes (and thus setbacks).
What I have found is that for the months of hard work I put in, I get
years of stress free living with a housebroken or potty-pad-trained dog! Yeah!!
Good Luck!