More days/ more often than not

The literal meaning of “more days than not” is most days, as in this sentence:

• Seattle gets a lot of rain. Actually, it rains more days than not.

This expression can also have the broader meaning mostly or usually. 

“More days than not” is not a common expression, however. The related expression, “more often than not,” which is another way to say usually, is much more common. 

Here are some typical examples:

1. More often than not, she arrived at school without her homework. 
2. When the kids were young, their father was gone more often than not. 
3. The most effective treatment, more often than not, is rest. 

Other expressions with the same structure include:

• More times than not (=most times) 
• More frequently than not (=most frequently)
• More likely than not (=most likely)

I hope this helps.