I didn't do one and my wait time was 17 days.
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RENEWAL Application Sent - 6/12/2014 by USPS Priority to Dallas (self-filed)
Confirmation text/ email- 06/18/2014 ~~Form I-717 arrived in mail - 06/23/2014
Biometrics appointment letter arrived - 06/26/2014 for 07/11
Approved i821 and i765 - 9/19 (EAD arrived in mail 9/27)