I have been sealcoating in the northeast for years. I believe that sealcoating will extend the life of a driveway. The thawing and freezing causes stress cracks where water freezes and breaks it up. The seal coat seals these cracks however at some point a new driveway is needed.
Concrete is very susceptible to salt, freeze/thaw conditions, and many chemicals, a good sealer will prevent salt, water, and chemical penetration and add to the lifetime of your concrete.
Silencure A is the sealer we use, it is an oil based sealer. With all the benefits previously mentioned with 2 coats it creates a water tight seal, but should be applied once a year.
Sealer is used to prevent any cracks, corrosion, stains, etc due to weather conditions and other various factors such as salt.