A project should be marked as completed at some point. It can have the people it needs and the routine to go through the customer acquisition, value, cash cycle. Once finished it can just have a routine that does a few updates here and there but is feature complete.
As someone who is finally getting serious about project management the real value is figuring out where to optimize limited resources. Not everything is equally important. Some tasks have a higher ratio of importance than others.
So a project should at some point be theoretically completed. It should have a cycle that is done and run in a mostly independent manner. And if it is software it should run with as minimal of resources as possible.