I guess this conversation might be unusual. But does the wife's question make sense to you? Let's suppose they don't have a timer.
Wife: How long have the eggs been boiling?
Husband: Six minutes.
Wife: They'll be done in four minutes. Please watch the time.
I feel the question isn't very right, because we usually say eggs are being boiled. In other words, I should use the passive voice.
But the passive sentence looks odd to me:
How long have the eggs been being boiled?
There's another option, the present perfect simple.
How long have the eggs been boiled?
However, it seems to ask how long it has been since the eggs were boiled well enough to be served?