Apologies if this has been asked before. Searched and couldn't find anything. Am 35K, fly a lot of flights in Q400's with my girlfriend. Up until now, had been choosing preferred seats, to sit together and guarantee luggage space. But realized with zone 2 boarding and due to neither of us being overly large, we don't really need preferred seats. All we care about is sitting together.

Do we need to choose advance seat selection? Or, since we booked as a couple, are we almost certain to be seated together once seats are assigned? If we generally will be seated together, what situations might arise that would make that not happen?