If you haven't paid for a Frontier seat assignment, you might not want to rush to check-in, as they seem to assign the worst free seats to the early check-ins. But I encountered a weird contra-situation last week. If Frontier needs to reduce the number of passengers on the flight -- like for strong headwinds -- they bump based on check-in time. It doesn't seem to matter if you have status or any other factor. I was flying with the Bundle (on my 2022 status) and I DID have a seat assignment, but didn't rush to check-in (did so 5 hours before the flight). I got very close to getting thrown off the aircraft. So definitely check in early if you already have a seat assignment.