This is a GREAT question! As simple and straight forward it is, it’s in fact loaded with infinite variables. How long is your hair? What color/shade? How fast does it grow? What is your diet like? Is your hair moisturized? Does it split? Break? What kind/quality products do you use?
There are so many questions that a clear answer is as subjective is an individuals taste is. A good rule of thumb is bi-weekly for a trim. This gives hair a chance to grow and is often the time when control becomes a little tricky. The shorter the hair, the more often you want to sharpen it up. The better the blend, the longer it lasts. The crisper the edge up is, the longer you can go before a clean up… and so forth.
One thing to keep in mind is potentially cutting too often (We all know folks that would get cut every day if they could!) Once per week is the maximum I would suggest. More frequent cuts and problems like hyper-pigmentation around the hairline, or unhealed micro abrasions on the neckline, unsealed cuticles, among other issues are more common to arise.
In short, visit the shop as often as you like. Take a look in the mirror, and if you need to be freshened up, go see the barber.. UNLESS YOU’RE ACTIVELY WOLFIN’!!!