I think, after mulling it over, that if one is honest, realistic, and open about their goals with partnering- AND the partner AGREES, then there shouldn't be a problem. It's a shock when after ten years, someone says "Ok, I'm throwing you over for this one because s/he's better"... instead of "I've gotten an offer, and remember when we talked before, about how if one came along... well..."
But if everyone's ok with it, heck yeah, collect 'em, race 'em, trade 'em!
PS: Someone needs to fix the apostrophes. They are being replaced with numerals.