As a rule, your residence permit is issued for the period of your stay at the UvA. In individual cases, you may wish to stay longer than planned (for example to complete your project). Before the actual expiration date of your permit, you can (and should) apply for an extension. The IND usually sends a letter three months before the permit expires with an application form included. Extension of your permit is your own responsibility; you can ask for assistance at your personnel department or SIO.