I prefer being paid bi-weekly or monthly, depending on the payout threshold. It sometimes seems like places want you to wait forever to get paid, and thus you might go a couple months without being paid since you didn't hit the threshold. This is rather frustrating to someone just building a site up not adding them to an established site with established traffic. I like a threshold of $20 or biweekly/monthly not being required both.
Monthly is fine, but all my affiliates pay between the 19th-29th of the month. Would be nice to have someone who paid around the 10th to ease the waiting period.