It is possible to get amaryllis bulbs to rebloom. In the commercial world I understand they recommend this:
After flowering cut off the flower, and when the stem droops, cut it right back to the top of the bulb.
Water and fertilise your bulb and leaves for six months, in order to keep the plant healthy.
When the leaves go yellow, cut them back and take the bulb out of the soil. Keep the clean bulb somewhere cool at 4C - 5C for at least six weeks.
Plant the bulb up again eight weeks before you want it to flower.
This is all quite complex and I haven't tried it myself so I don't know how well it works. However my dad has some amaryllis that are years old. Most years they only produce leaves and he adds some very realistic flowers that he found in a charity shop!