Probably not, the best part of 愛 is coming to realization that あなた want to be with this person forever, and that あなた want to end up with them.
But if あなた know, i'd think it'd kill a lot of the relationship, i mean you'd know you'd end up together, so why bother with all the wooing and courting.
Yes.I would then at least know I won't be lonely my whole life. It's just not good enough having someone tell me that there's someone out there for me.