A couple of points : - We are each suited to different things. There is no one answer that will work for everyone. - In my case, I feel if you live together for long and don't get married, there is a good chance that could affect the relationship adversely, especially if one of the partners is interested in putting a definition around it. I am all for live-ins. But I fear it wont work for ever especially if s/he wants to get married. - To answer your question , a reliable companion, as I see it, is someone who is obliged to and can give you their undivided attention when you need it. I have many friends but I don't think I can call them and pour my heart out to them. Sure when you are 17 you can do that but at some point your circle of friends becomes smaller and smaller. Who are you going to go to for emotional support then? And don't tell me you dont need emotional support - we all do - it just the degree that varies.