Extending college for more than four years not only increases the cost of tuition and student borrowing, but it can also dent income and retirement savings, a new analysis finds. Graduating on the “five-year plan” may be a running joke for many college students. But that outcome can eat away at a student’s chance for financial stability, according to an analysis published on Tuesday by the website NerdWallet. That’s because when students are in school for an extra year or two, they pay more in tuition and debt and are not earning a salary or contributing to retirement savings.