Training with a Clicker vs Clicker Training

I'm confused about this, because I thought that the click was supposed to become a conditioned reinforcer and that you always "mark" when the dog did what you wanted, but fade the treats down to occasional and random (as well as giving other rewards like praise and scritches) so that the dog doesn't only perform when they're hungry. I thought unpredictable reinforcers were actually better at getting a behavior than predictable ones, once the dog has actually learned the behavior.
(The trainers I've worked with used verbal markers rather than clicks. I don't know if that makes a difference in terms of when you need to treat.)
KellyK, Lehrhund: Dog Training Law

That is a very common misinterpretation. It does work, at least for a while, but you usually end up having to recharge the clicker pretty often. I consider it an inefficient use of the tool.

Instead of fading rewards, think about raising criteria.

Example: If your dog can do a five minute down stay, you aren't going to click 30 second stays (unless you're fixing something). When a student is in an algebra class, they don't spend time doing basic subtraction except in the context of a harder problem (like every 5 minute stay includes a 30 second stay). If your student CAN'T do a 30 second stay or a basic subtraction problem, they have no business doing advanced work when they don't have the foundation to be successful.

Clickers are really most useful in behavior acquisition. See shaping, where the goal is crystal clear communication. By the time I've put a name on a finished behavior, I usually do not need to be so precise about what I'm reinforcing, so I switch to a verbal mark. At that point, it's a matter of context, timing, and ability to reinforce that determines if it is worthwhile to mark.

Example: You are in training and working on down on recall. Let's say your dog knows this exercise, and does it with confidence. In other words, it's just practice, you aren't fixing anything. When he downs, you might offer a word of praise ("Gooooooood dog") before finishing the recall. It's not appropriate to mark in that situation, because you don't want to end the exercise, but it is appropriate to let the dog know he performed the criteria.

When he fronts and finishes, you can mark and reward, or can release, or you can move into the next exercise. It depends on how the dog was trained and what he needs. Both of my dogs have a tendency to bypass front and auto-finish, so I rarely finish them in practice and often mark and reward the front.

Another note about rewards: I prefer to have a wide range of reinforcers that I can use very often than one reinforcer used sparingly. Developing life rewards and self control (sit to go out the door, heel past the squirrel to chase the squirrel, give up the treat to get the treat) are the key to clicker trained behaviors being useful in real life.

You are right that unpredictable rewards create stronger behavior than predictable ones (compare buying a soda from a vending machine vs playing slots at a casino) but many people get so hyper focused on getting off food rewards that they miss the bigger picture of using rewards in training. Clicker training uses a LOT of food, particularly early in training, and I think people see that and think they're going to have to keep up that rate of reinforcement for the life of the dog. You won't, I promise, even though it looks that way from the start.