You will likely throw a lot of calls away if you are doing a lot of experimenting with call designs. However, once you begin to focus in on designs that work, you can pretty much make call after call that "will hunt".
The fun in making your own calls is in searching for the "holy grail" in a mouth call,...one that makes you the best caller you can be. I have dozens of calls that I am happy with and would take to the woods,...but I am always looking for one that sounds just a little better. Because of that, I throw a lot of calls away that are perfectly good hunting calls.
The one real problem with mouth calls is that you can't give them to someone else after you have used them,...few people are comfortable with using a hand-me-down mouth call,...even if it has been disinfected. Therefore, a lot of good calls end up in the trash.
But to answer your question directly,...when I started making my own calls, I probably threw away 25% of them pretty quickly,...and the majority of them within a year. Nowadays, because of the cutting process I go through making calls, it is the rare call that I throw away because I couldn't find the "turkey" in them.