Too much territory for them to investigate will only cause trouble if you can't be there to correct them. Also get a good cleaner one that will neuteralize the spots where they have gone. Not one that will just cover up the odor. Remember dogs can smell up to 100+ times better than us. (Often when a smell is up to 6 months old!!!)
Best way to correct a dog is when he/she is in the middle of
using the rug, sofa, etc. Yell "NO!" and immediately put them
outside for them to go potty. ALOT of praise when they go out-
side will also help. "Good dog going potty!!!" DO NOT rub their
faces/nose in the mess they have made. Do not yell at them when
you come home to find a mess. They will have no idea what you are
talking about and will soon become fearful when you arrive home.
Dogs do not have a long attention span and can only associate a
bad action with a correction for less than 2 minutes. You must
catch them in the act for it to really click in that you do not
want them to use the house to soil in. Keeping their schedules
of feeding, water, and letting out also will help. Good Luck!