The last time I checked my feet were still planted on planet earth. Legally, if you have not conditioned your abstracting orders upon your receipt of payment by your client, the abstractors are entitled to timely payment. If no date of payment is specified in the search order, payment is due within a reasonable period of time determined by course of dealing between the parties or  industry standard. I think it is safe to say that most of the abstractors requesting payment in this thread expected payment within 30 days. If as you say, you have to accomodate your clients' pecadillos with respect to payment, you may need to adjust your business model or at least notify the abstractors up front to give them the opportunity to decline the order.