Do I have to keep using the clicker forever?

No, you don't have to keep using the clicker forever.

After a few training sessions, when your dog is reliably performing the behavior on cue (every time you give the command), you can stop using the clicker. In other words, once your dog has mastered the behavior you can stop using the clicker.

The clicker is only used for teaching a new behavior and perfecting it. Or for brushing up on a behavior that wasn't mastered in the first place.

The clicker is a tool for communicating and pin-pointing to your dog what behavior will earn him a reward.

So as soon as he's mastered the behavior, the clicker has done it's job, and using it is no longer necessary.

Next: Do I have to keep using treats?