The flowers of many orchid species persist longer than those of most plants, however, they do not last indefinitely and eventually wither and fall off. New flower buds sometimes form on the old flower stalk or a new stalk may emerge. The particular habit in this regard depends upon the orchid species. If you know the plant's species, you should be able find care instructions on the Internet or in a reference book.

With proper care, orchids live for many years, so if yours is healthy there is no reason to dispose of it.

Go here for reliable information about growing orchids:
https://extension.illinois.edu/hortihints/0204d.html