Figment's Friends is correct. You can add the "no-expiration" option on to your 10-day anytime before the 14th day following its first day of use. The cost will be $100+tax. If you have only 1 or 2 days remaining, it will not be worth the expense, since a 1-day pass costs only $63.63 and a 2-day costs $126.74. However, if you have "pluses" or have more than 2 park days remaining, it might be worth the additional cost.