We have two cats who have the run of the house. They are strictly indoor cats and the only time I contain them is if we have people coming in & out of the house who might let them out accidently & then we put them in the old bathroom.
Funny thing - occasionally our older cat, Pip sneaks out when my husband goes out. We used to get upset and go out & chase around. It turns out, the cat goes out for about 5 minutes and comes back & knocks on the door, kid you not! He pats the screen door hard to let us know he is back & wants in!