How many です can there be?

[Leng Chuan]

While reading about the usage of　だ　and ですfrom a website, I was told that ですcan only come at the end of the sentence, except when you're directing quoting someone. However in one of Japanese101's podcasts, I heard something along the line of this:

でも、今蒸し暑くて、夏ですし、もうだるいです。


So, how many times can we mention です?

[Psy]

Yeah, I had a textbook that mentioned this as well, and while it's probably true from a grammatical sense, in real life, people throw in the polite forms mid-sentence all the time, particularly in more formal situations. Even if it isn't entirely correct, since the natives do it, I'll just say「郷に入れば郷に従え」 .

For the record, 「でも、今蒸し暑くて、夏だし、もうだるいです。」 is also a perfectly fine, polite sentence.

That's all I know!