Most horses need to get their hooves trimmed every 6-8 weeks. However every horse is different. Some horses have more sensitive or brittle hooves meaning they are more prone to cracking and chipping. Thoroughbreds especially are like this. It also depends on how often you ride, as well as where you ride. If you ride on really hard surfaces such as pavement, the hooves wear down more easily. If your horse seems sensitive when walking on different terrains and surfaces, then he/she may need shoes. Shoes make walking more comfortable for a lot of horses. There are many horses though, on the otherhand, never need shoes in their life. It really all depends on the horse. Regardless of whether you shoe your horse or not, regular trimming is essential. Hope this helps!
And yes, you put your question in the right spot. =)