I have had both indoor and outdoor cats, although they have all, always been indoor at night. Some have had to adapt to indoor when they were previously outdoor. Most do not mind. If they have never been outdoors there is no compelling reason for allowing them out, and a lot of compelling reasons for keeping them inside - less risk of RTAs, fights, infectious diseases, poisoning or deliberate cruelty (see the thread 'entitled my cat has been shot...'. So, for me, I would have them indoors all the time if possible, though having said that, my present lot will probably be outdoor once Smidgen has his microchip embedded as they will be company for the dog, and keep him distracted from the fox who has taken up residence over the back fence.