You can request payout at any time -- just click the "request payout" button on the affiliate program page. Once you've received an email notification that your rewards are ready, go into your eWallet account and let them know how you would like to receive your payment and BOOM. Money in your pocket.
NOTE: eWallet does charge a flat fee for every payout. We highly recommend letting your balance build up on your affiliate page and requesting a large amount all at once.