That's a good question. I take my clickers to class and sometimes on walks or other public places. Even though Sundog picks up the initial trick quickly, I am always working on the 3 D's, which can take quite a while to perfect and I am clicking a trick for a long time. I often work on variations. Sometimes I am working on capturing. I am also prone to the occasional spontaneous short training session. Sometimes I don't remember where a certain clicker is, but I know where another is. I don't like having to hunt down a clicker. I always have more than one in my class bag, so that I can lend one to a friend if I need to. And sometimes I actually lose one or just can't find it. It just works better for me to have more than one clicker and I know there are times when I didn't have one handy and I would have liked to have had it handy. I'm interested in what more experienced (or less experienced too) people might have to say on this subject. I usually have treats in my pocket too. Everyone thinks it's kinda' funny when I work on recalls in the woods while off-leash hiking using rewards and the premack principle, but it works. Even if I don't have a clicker handy, I can usually still mark and reward.