I have known people who never even change the oil, just filter it and add more as needed. I think that’s kind of nasty though. It makes the food seem more greasy and it tastes bad.
Depending on the type of oil you use, and your volume, and what you are frying, it will go from a light golden color to brownish in a day or so.
Filter it every day, and if you use it a lot, filter it once per shift. When it starts to look "too dark" and smokes at your fry temp, it’s time to change it.