For tobaccos and NETs I can get a few days. Fruit and florals around a week. For SOME juices though, especially the sweet ones and the desserts that demand a clean wick to taste the nuances, daily.
As Ryedan mentioned, less is more at least until it's not. Honestly the frequency at which cotton wicks need to be changed, in my experience, is ENTIRELY subjective to what juice you're using. This will most certainly vary from vendor to vendor, and even juice to juice in the same vendor's selection.
If you've got a particular flavor that requires daily changes I'm afraid the only answer is to oblige. Like others have said, it takes only a minute and your vape will be all that much better.