I actually plan on ending it. A story with a beginning and end is easy to follow. If you don't have an end to the story, then you're going to be in a loophole, trying to figure out where your characters should go and what they should do.
Spoilers if you haven't seen the first trilogy of Star Wars!
It's like Star Wars. That has a beginning to end. From A New Hope to Return of the Jedi.
- Luke Skywalker starts out as a simple farm boy, wanting adventure. He is called to action when his relatives are killed. He then journeys on to save the Princess with his Mentor and new Allies. This leads to him joining the Rebellion against the evil Empire.
- After he destroys the First Death Star, he is called to train with a new Mentor. Then he faces the Ultimate Evil's right hand man, Darth Vader. Turns out, he is Luke's father. O_O
- After escaping Vader, Luke trains once more, and becomes a mature Jedi. He then faces the Ultimate Evil which is the Emperor. But after his father saves him, the Rebellion wins and the Empire is defeated.
It's always good to have an ending, so after your readers been through the journey with your characters, they can be at peace and know that they had a fun ride. Some endings are good, some tragic. But all that matters is that your readers had a great time with the characters and the new world they experienced.