The " four years" is used in two different requirements ---(a) first four years of post secondary education - education year classification , not duration and (b) Not have claimed AOTC or Hope for more than 4 tax years. Below is quote from the IRS:
"To be eligible for AOTC, the student must:
- Be pursuing a degree or other recognized education credential
- Be enrolled at least half time for at least one academic period* beginning in the tax year
- Not have finished the first four years of higher education at the beginning of the tax year
- Not have claimed the AOTC or the former Hope credit for more than four tax years
- Not have a felony drug conviction at the end of the tax year "
Hope this closes your query / worry --- Good Luck
