This will depend on a few factors. A big one is local weather conditions. If you live in a climate that’s prone to snowing or dust storms, you’ll have to clean your windows more often. Whether you live in a rural or urban environment can also have an effect on them, as well as whether or not you live next to a body of water like a river or lake.
Personal preference is a factor: some people want their windows to always be clean, so they clean them weekly. Other folks may not mind a little dust, and may do it once a month. Location is also important. If your window is facing a stunning view outside your home, that’s a good motivator for keeping it clean so you can showcase it and enjoy it. And of course there are special cases where you’ll want to clean your windows because of circumstances beyond your control.
The truth of the matter is that there isn’t a magic number for how often they should be cleaned. You know your windows better than anyone else, so see how often they get dirty and what kind of care they’ll need. Just be sure not to neglect them. Overtime both the glass and frame can deteriorate if they aren’t cleaned and cared for properly. Cleaning a window is much cheaper than having to replace the window itself.