The work doesn't end with implementation. Ideally, the maintenance phase lasts until the system is no longer in use. During the maintenance phase, the system is monitored to ensure that it continues to work properly and meets expectations. If any errors (or "bugs") are found, they are fixed. Also, as requests from users come in, they are analyzed and the system is modified to accommodate any new needs which may arise.
If the new needs cannot be met by the original system, the cycle starts over to design a significant modification to the system or to implement a new system. The first step of the new Systems Development Life Cycle is the Planning phase, which focuses on the overall system changes that need to be made. The SDLC continues through each phase until a new system is in place that meets the needs of its users.