What phase in the SDLC is described as the longest and costliest?

The maintenance phase of the Software Development Life Cycle (SDLC) is characterized as the longest and costliest due to the continuous need for updates, bug fixes, and enhancements after the software has been deployed. During this phase, the software is actively used, and real-world issues may arise that were not anticipated during earlier phases.

The maintenance phase often requires ongoing support, adjustments to meet evolving user needs, and may involve integrating new technologies or adapting to changes in business processes. These tasks can lead to significant resource allocation, both in terms of time and costs, as teams need to continually assess and improve the product based on user feedback and operational performance.

Engaging with user support issues, performing regular system updates, and ensuring compatibility with new hardware or software environments can also contribute to the substantial expenditure associated with this phase. As a result, it typically surpasses the costs and duration of earlier phases, emphasizing the importance of careful planning and resource management during the initial stages of the SDLC.