I've used another variation on multiple life cycles, especially for larger projects where the project staff or project management didn't want to or know how to use an agile life cycle. This combination life cycle has two incremental pieces. The developers (at the top of the picture) use Staged Delivery.
Since this is not an agile approach, the testers work separately from the developers. See their approach, Design to Schedule, at the bottom.
Here's the issue: when the project separates the developers and the testers, management often decides that when the developers are done, so are the testers. Except, we know that the testers cannot be done, because they lag the developers.
Design to Schedule helps manage that problem. The testers keep up with testing as much as possible. If someone decrees the project is “done,” the testers have “finished” all the testing to date. They don't have partial bits of tests—they know what they've done and have not yet done.