“The effectual fervent prayer of a righteous man availeth much.”
It is true that God doesn’t need you to pray for hours on end before hearing you. However, this does not undermine the place of diligence in the place of prayer. There is a spiritual discipline that staying in the place of prayer births in you which is necessary for your spiritual growth.
You see, prayer doesn’t change God per say, it changes you. It makes you make attuned with the things of the spirit; more sensitive to your spiritual environment and what God would have you do per time. I remember the first time I tried praying for an hour; this was several years ago. I had prayed all the prayers I knew to pray and thought that one hour was up already, only to realize that I had only prayed for seven minutes. But I kept at it, and now many times I don’t even know when one hour has skidded by during my prayer time.
You have to be willing to go the extra mile in your spiritual walk. Not so that you can prove a point to God or try and be holy. But because you’ve already been approved by God; you’re already holy. The Holy Spirit is at work on your inside, and so you have no excuse not to give your spiritual growth your greatest commitment.