• A borrower may change to the ICR plan at any time. After the change, the borrower’s repayment period will be a maximum of 25 years. If loans are not fully repaid after 25 years of repayment, any unpaid amount will be forgiven. The maximum 25-year repayment period may include prior periods of repayment under certain other repayment plans, and certain periods of economic hardship deferment. The forgiven amount may be considered taxable income. (The ICR Plan is NOT available if you have a Direct PLUS Consolidation Loan(s) made before July 1, 2006 and/or a Direct PLUS Loan(s). However, you are eligible to repay any Direct Consolidation Loan(s) made on/after July 1, 2006 under the ICR Plan even if it includes a PLUS Loan(s).)
• A borrower may change to another plan as long as the new plan has a repayment term that is longer than the amount of time the borrower has already spent in repayment. The new repayment term is determined by subtracting the amount of time a borrower has spent in repayment from the term allowed under the new plan.

Source: U.S. Department of Education