The IRS website mentions degree several times, "Be pursuing a degree or other recognized education credential", so my guess is the first 4 years pertains to a 4-year degree. However, the IRS's website says this: "Academic Period can be semesters, trimesters, quarters or any other period of study such as a summer school session. The schools determine the academic periods. For schools that use clock or credit hours and do not have academic terms, the payment period may be treated as an academic period."
So my guess is, if you finished a 4-year degree before 4 years, it still counts as 4 years. I went to a College that had only 2 terms. Each were 6 months long, but I could finish as many courses as possible, and earn as many credits as I wanted to. If I finish the degree in 2 years, I probably would not qualify for the AOTC. The IRS's website often refers to the AOTC for undergraduates also. So, to clear things up with others that have questions, you can only assume that any student that has a 1098-T, has not graduated (4-year degree), and attended college at least half time, qualifies for the credit.
