Question

A typical proposed amendment to the Constitution is given how many years to be ratified by the states.

Answer 1

On the 18th amendment, the Supreme court stated that  states must ratify a proposed amendment 'within reasonable time', but the time never been specifically defined

For the 18th, 20th, 21st , and the 22nd amendments, The congress set the ratification processing period at 7 years
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Answer 2

Although there has been no determination as to how long a ratification process may take, the Supreme Court of the United States has said that ratification must be within "some reasonable time after the proposal".

Ever since the 18th amendment, Congress has traditionally set that period at seven years. Therefore, a typical proposed amendment to the Constitution is given seven years to be ratified by the states.