If you keep the amaryllis bulbs outside they will last a year or longer.
But if you keep the amaryllis bulbs inside the house in a pot then they will typically last from 4 to 12 weeks with proper care.
During the winter your amaryllis bulbs will go dormant as well and do not need watering in the winter but in the spring and summer you'll need to water the amaryllis bulbs to make them last.
You can also store the amaryllis bulbs in a cool dark place after digging them up which will help them last a bit longer than being out in the sun all the time.
The amaryllis bulbs will also start blooming six to eight weeks after planting