When products are operated for a given time t, not all of the lower-indenture items that make up the product necessarily operate for the same time t. For example, the landing gear mechanism of an aircraft is only activated one after takeoff and once before landing. During a flight, a pump may only operate a few times for a few minutes each time to maintain a charge on an accumulator. In such cases, the percent of time during which the item operates is called the duty cycle. An item having a 50% duty cycle only operates for 50% of the total product operating time.
產品操作一段給定時間 t ，不是構成產品的所有低階層物品都需要操作時間 t。例如，飛機起落架機構指在起飛後、降落前各啟動一次。在此狀況，物品操作的時間比例稱為工作循環，當一個物品的操作時間只是產品操作總時間的一半，稱工作循環為 50 %。
B.1.1 Purpose
目的
Basic constraints on design practices are design life and operational and environmental profiles. Life cycle planning considers what design approaches should be used to ensure that a product will perform reliably throughout its useful life, given the exposed characteristics of its end-use environment (operation, storage, shipping, handling, etc.)
設計壽命及操作與環境輪廓為設計實務的基本限制，生命週期規劃工作考量使用何種手法，可以確保產品在其有用壽命期間內，在給定最終使用環境（操作、儲存、運送、搬運等）的曝露特性下能夠可靠地使用，
B.1.2 Benefits
利益
Life cycle planning provides an assessment of the "big picture" in determining how to most effectively (reliable performance over the life of the product) and most efficiently (minimize product cost) meet the long-term needs of the customer. Through life cycle planning means that product designers are aware of the imposed constraints (performance, reliability, cost and schedule) and will use only those value-added design approaches which will meet those constraints.
生命週期規劃提供一個評鑑用的大藍圖，決定如何能夠最有效果（在產品壽命期間有可靠的績效）及最有效率（最少產品成本）地滿足顧客長期的需要，藉由生命週期規劃方式，產品設計人員可以熟知外加的限制條件（績效、可靠度、成本、與時程）下，以及使用一些既可以滿足這些限制條件又具有附加價值的設計手法。
B.1.3 Timing
時機
Product life cycle characteristics need to be defined early in the Concept/Planning phase. Preferred design approaches cannot be selected, however, until the customer needs (or requirements) are thoroughly understood (through techniques such as market surveys or Quality Function Deployment (QFD)), and the expected end-use operational and environmental profiles have been analytically or quantitatively measured.
產品生命周期特性需要在概念與規劃階段初期完成定義，只有在（透過市場調查或品質機能展開）完全瞭解顧客需要（或要求），以及經由解析或定量量測得到預期的操作與環境輪廓之後，才有可能決定優選的設計手法。
B.1.4 Application Guidelines
應用指導綱要
In designing for reliability, life planning activities should include the selection and analysis of materials, parts, components and software (and their respective suppliers) that will meet product life requirements. Tasks that can directly impact this aspect of product hardware design, either through direct selection or trade studies, include: Environmental characterization, Thermal Design (high level), Dormacy Analysis, Durability Assessment, Design of Experiments (DOE), and Accelerating Testing.
當設計可靠度時，生命規劃活動應該包括選擇及分析滿足產品生命要求的材料、零件、組件與軟體（以及其相對供應商）。這些會直接影響產品硬體設計的工作項目，不論是直接選擇或是經過權衡研究，包括：環境特性決定、熱設計（高層次）、惰態分析、耐久性評鑑、實驗設計(DOE)、和加速試驗。
Effective and appropriate application of these tasks will result in (1) a realistic assessment of the conditions under which the product is expected to operate and (2) a means of evaluating materials, parts and components as being suitable to withstand the rigors of the end-use environment. Establishing derating policies, fault tolerance approaches, and critical item definitions will also help define which materials, parts, components and software should be selected to ensure satisfactory design reliability. Once the design approach has been selected, life cycle planning can be extended to include those tasks which will assess progress towards meeting the design reliability requirements, measure the level of achieved inherent reliability and ensure that the inherent reliability of the product isnot degraded through subsequent production / manufacturing processes and customer use.
有效地且適當地應用這些工作項目，可以產生的結果包括：(1) 在預期的操作條件下實際評鑑產品，和(2) 評估材料、零件與組件適用於抵抗最終嚴苛使用環境的方法。