First, what does John 17:4 have to do with your question?
Secondly, to answer your question: I'm not sure it can be answered. For each assembly is accountable to its own elders, and each set of elders is accountable to God. I don't think we can adequately answer this question in general.
But from what I have observed, there are elders who do, and elders who don't. The elders who don't think they do.
Let me explain: It's not simply enough to "give time and opportunity" to the youth. Many of the elders who don't use youth but think they do often fall into this trap. They think by giving opportunity that they are using the talents of the youth. Sure, the youth are being used, but is this effective?
The correct way, if I may be so bold, is to invest in the youth by discipling them and training them. Discipling takes great effort and time. It means to spend time with them, and understand them . It means to try to think like they think. This is not just the elders job. But all older men in the assembly are to take younger men and train them. Older women are to do so also with younger women. Each of us should have a timothy and ideally should also have a Paul. That is we should be training somebody, and we should be trained too!
I could go on and on on this topic, but time does not permit. Unfortunately, Br. Ponmanissery, the answer to your question is not easy.