when using idioms id OUT OF THE QUESTION

[LadyMary]

Thanks to this site, we've already learned a lot of new idioms. So I've got a question for you!

When do you think using this new knowledge is out of the question? When using idioms is out of place?

[LadyMary]

for example, I’ve learned recently that the idiom “it’s raining cat's and dogs” is now used by pensioners only!..so, I’d rather erase it from my memory not to look stupid)))

[Anglika]

The only time an idiom should be avoided is when it is rude or impolite. But be careful only to use those you understand and in the context that is correct.

Raining cats and dogs is not restricted to pensioners [yet]!

[Tdol]

Pensioners and non-native speakers.

I think you have to be take your audience into consideration- will they understand? Also, using a lot close together can come across as a bit artificial.