It depends on the type of terrain (rocky or not rocky), type of soil (sand vs dirt) and diet.
All of those things = how fast the hooves grow or wear themselves down.
My horses get trimmed every four weeks because they all grow hoof really fast and I have two with insulin issues. Insulin issues affect the hooves (think Type II diabetes in humans) and hooves belonging to these types of horses cannot be mis-managed.
If I am to take your Forum name literally, it sounds as if you are not used to having horses and someone has tread on your kindness to let them keep their horse on your property
If that is the case, you are probably clueless as to who is a good farrier/trimmer in your area and who isn't. Anyone who needs your business will lie and convince you they are the best and after they're done trimming you won't know the difference, simply because you're not familiar with how hooves should be trimmed
If you are fortunate to have more than one large animal vet in your area, I would call everyone of them for recommendations. Explain your situation because, as a rule, vets don't like to do that sort of thing, but they make exceptions.
Hopefully you would get more than one reference for the same person
If your instinct is telling you the horse needs a pedicure, then it needs one since I have yet to know of any woman whose instincts aren't spot-on
Good luck with this, as it seems you have inherited a horse, like it or not
Please feel free to ask a lot of questions