Extending the life of a product through remanufacturing or refurbishing is generally regarded as being "greener" than new production, as it avoids the resource consumption and waste generation associated with the new production; however, when considering improved performance of new products, extending the lifetime of less efficient, less productive old products may not always be greener than new production. Shortening the product's life by early replacement with a newer, more efficient product can be a better option, as "Cash-for-Clunker" programs have claimed. This paper presents a generic model to decide optimal lifetime strategy for a product. Three different lifetime strategies-To maintain, to extend, and to shorten the current lifetime-Are compared from an environmental perspective, for a given time horizon. The average environmental impact per unit production is used as the basis for a fair comparison. Applied with an optimization technique, the model can also identify the optimal lifetime length of a product. To illustrate, the developed model is applied to an example of complex heavy-duty, off-road equipment.