It is so difficult to choose. It would be like choosing to live with only one woman (man) for the rest of your life. The thing that makes living with one mate as opposed to one bike is that the laws and taboos help things along. What helps the most is that your mate actually is capable of loving you in return - something that no bike, no matter how extraordinary has ever done.
I'll just stick with one mate and several bikes. My wife is of an age that she is of the on topic and classic vintage.
Garth Libre happily spinning off the miles of his life with Bianca Pratorius in Miami Fl USA (and all the women on this list will say "Oh, how thoughtful of him to say these nice things". The men will think me a terrible bore and big suck up.)