Mrs. Corriveau has just retired at age 58 with $160,360 in her RRSP. She plans to live off other savings for a few years and allow her RRSP to continue to grow on a tax-deferred basis until there is an amount sufficient to purchase a 25-year annuity paying $2000 at the end of each month. If her RRSP and the annuity each earn 7.5% compounded monthly, how much longer must she let her RRSP grow (before she buys the annuity)?