Future perfect continuous tense and its usage!

By the time when you have been singing for 7 years, she will have been singing for 14 years!

I wonder whether it is a congruous sentence!

Hello,
The grammar in this sentence is correct. However, you need background in order for it to make since. For example, She has already been singing for seven years, and you have just started. Therefore, by the time you have been singing for seven years...

It would also be helpful to explain why this is relevant. Is this person trying to compete with the person who has been singing for longer?

I hope this helped

I think it should be

Would is used when you are talking about the future scenario when you are talking about it from the perspective of the past or present.. This line talks about the future here.

I am not sure about th usage of when here too.

My 2 cents.

A couch that everyone longs to sit on.

I will be sitting on the couch and looking at my friends. I will be standing up when my friends will be approaching the couch.

My question is should i apply the first conditional to this sentence or whether it is possible to rely on the first conditional when we talk about the future actions .

i will stand up when i see them approaching the couch.

Both sentences should be in the future.

"I will stand up when I see them approaching the couch" Sounds better.
The first option is too wordy and awkward. Hope this helped