What's the main difference between "as usual" and "as always"? Or are they interchangeable?

Native speaker’s answer
Rebecca
The main difference between "as usual" and "as always" is that "as always" implies that every time something happens, it happens the same way. Or something is "always" the same. I'd also say that "as always" is slightly more dramatic than "as usual" with the emphasis on "always". Whereas "as usual" means that it habitually or commonly happens that way. Maybe not <every> time, but most times. Between the two, "as usual" is most common. Ex: As usual, Tim is late! Ex: He was rude, as always.