This will be based on each athlete’s personal experiences and type of workout, but some pairs last for almost two years. This also depends on the type of glove, as well. The material the glove is made with will add to the durability of the glove. If you’re concerned about having to replace it, consider the warranty and see if they offer a lifetime guarantee or manufacturer defects.
At the end of the day, however, you should feel like the best CrossFit gloves for you will last you as long as you need them. I have had my WOD nation gloves for over a year now and still don't have a need to replace them. I might get another pair of WOD nation's next year since they will have more wear and tear by then--but from what it looks like now, they will probably still be going strong!