I suspect that this is the answer you wanted to hear: "No. Don't bother to learn that! It's boring and difficult for you, and it's boring and difficult for us too. We never use it anyway. It's far too complicated. You can forget it." Well, sorry, but that's simply not true. As Andrew says, it's common enough. All our tenses serve a purpose, and if we need to say something in the future perfect passive, we say it. If you take your coat to be cleaned and you ask if you can pick it up on Friday, the employee at the cleaners' may well say 'That's fine. It'll have been done by then.' Nothing formal. Nothing complicated. If that's what we need to say, that's the form we use. But just because you've been taught more complex grammar, don't think that you can neglect the simple structures. "How often Englishmen use of tense...?' isn't a question, is it? I'm sure you learnt how to construct questions when you started learning English. Don't be so busy worrying about complex grammar that you forget how to ask a simple question! And one more thing: Do you really mean 'Englishmen?'. That's a very small group of people. English is spoken as a native language in the USA, Britain, Ireland, Canada, Australia, New Zealand and South Africa. Within Britain, not everyone's English - some people are Scottish, Welsh or N.Irish. And even in England, only the adult males are EnglishMEN. The rest of us are women, believe it or not. Or, in other words, of the 360 million native English speakers worldwide, only around 20 million or so are 'Englishmen'. It might be more inclusive if you said 'English speakers' - that would include the 300 million of us who aren't Englishmen!

It's common enough to warrant it being learned, yes.