There's no such thing as forever for them, not in their line of work, death is always too close for comfort, the world is not a safe place, they know that better than anyone, they can't even say there'll be a next Tuesday so they don't promise anything except as long as they're got, 50 years or 50 seconds it won't matter it will have to be enough, so Jo wears a white dress and Dean's bowtie itches but it's perfect because Jo says 'i do' and Dean kisses the bride. They don't have forever but they have each other.