A typical sump pump will usually last anywhere between 5 & 7 years. When replacing, you should replace it with the same HP rating unless your pump has a difficult time keeping up with water to be ejected. As for the backup system, that would depend on the amount you are willing to spend and how much water you want your backup to eject. The higher the GPH, the higher the cost. However, you should just think of it as cheap insurance.