A general rule of thumb that many runners stick to is to change your shoes every 300 to 500 miles. However, this largely depends on the overall wear and tear they have once you get to 300 miles, and is dependent on you and your particular running style. For example, if a shoe is made to have more padding and support for your heels, but you land harder and push off harder on the ball of your foot, then the shoe will probably need to be replaced sooner than a shoe that has more padding and support in the forefoot area. And there's also the budget to consider. If you are training for a marathon and running upwards of 50 to 60 miles a week, then buying new shoes every few months just is not practical or feasible.
Pay attention to how the shoes are holding up over time. Look for things like the loss of tread or traction on the bottom of the shoes (especially for shoes like the Hoka One Challengers, which are designed to be more of a trail shoe and so will have a better grip on the bottom of the shoe than other road shoes). Another factor to consider is how well the shoe is absorbing shock. When they are fresh out of the box, shoes will have a "spring" to them, to help propel you forward. Over time after repeated use, shoes tend to lose this spring back. And finally, if your feet start to hurt or you experience a sort of dull ache, it might be because your shoes have lost some of their support. These are all signs that it is time for a new pair of shoes.
As far as the Hoka One Challengers are concerned, they will likely last you closer to 500 miles because they have soles and padding that are quite thick and durable. Plus, they are made to withstand the intensity of trail running and can be put through a lot before they need to be traded out. (For more information on the Hoka One Challengers, see our article here!)