Garage C is great. I've used them for longer trips. There's also a new parking garage that will be opening in conjunction with the commuter rail station. The whole complex is connected to the airport via a skybridge (I think with peoplemover) over Post Road. Since you're going in February, that should all be open by then and may be another option for you. Since I don't have a garage of my own, I've used Garage B on a couple of occasions to avoid having to excavate my own car from snow. There's an internet coupon that makes Garage B cheaper than Garage C for shorter stays.