DL makes schedule adjustments almost every Saturday. Of course not every schedule is impacted, but for a trip in March, I would expect at least 2-3 schedule changes between now and then. They might be significant, but they also might be minor (such as a time change of only minutes or a flight number change). I would keep a close eye on your booking to make sure any changes DL makes filter down to your booking made with Chase as 3rd party reservations can take some time to update. You can compare your existing reservation with making a dummy booking on the DL website. You shouldn't have any "risk" per say of having booked through Chase, just maybe an extra step if any changes are significant enough to require rebooking. Normally DL will require you to make advance adjustments through whatever party you booked with up until day of departure. That step alone is why I generally advise people to always book direct with your airline, hotel, etc. But in cases like this where it was significantly cheaper, the extra potential hassle can be well worth it.