Final answer:
The best practice for law offices is to send billings regularly for consistent cash flow and to maintain good client relationships. Billing when the firm has bills to pay is not a recommended approach.
Step-by-step explanation:
The recommended billing practice for law offices is to send billings regularly. This approach ensures a consistent cash flow and helps maintain a professional relationship with clients by providing transparency regarding legal fees and services rendered. It also avoids creating a financial bottleneck by relying on sporadic billing to meet the firm's own financial obligations. The book's statement suggesting to bill when the firm needs to pay bills would not be considered a best practice in financial management for a law firm.