She may not ever leave you, in reality you don't want that but in fantasy it is arousing. You are also sharing her with men that might be more fit then you, have a bigger cock, fuck her better. For most of us cuckolds we want her to be more sexually fulfilled. Otherwise what would the point be if she is having worst sex than with you? No together you make sure she is having better sex. Then there are emotions and connections. For the right man she will start feeling them. That new relationship energy. A blend of cuckolding with polyamory. If you are lucky, if you are everything she needs you to be as the cuckold you won't lose her. It will feel that way sometimes though as you explore and play this game.