If you only pray few minutes daily then you are not doing anything spiritually
As pointed out there is definitely not a formula of exact times to get results with God, etc. But we do have to be honest with ourselves that many find it hard to have seasons of long prayer with the Lord, waiting and prevailing with God. Any of the godly men featured on SermonIndex are those who have daily walks with God in private prayer.
In the underground Chinese church there is one family church network that all the co-workers pray for 2 hours a day. It is basically required there as being a full-time worker. Most of the underground rural Chinese family churches pray for 1 hour at 5am everyday. This is a practice they do and find it important to their devotion to Jesus Christ. And the results are evident that the Chinese Church is growing very fast and spiritually their are disciplined and counting the cost with the Lord.
Would it not do good for the North America Church to pray more and seek the face of God saying no to the flesh. I take this as a conviction to seek to pray more before the Lord, who empowers.
"A boy who rises at 4:30 to deliver papers is ok, but to urge our young people to rise at 5:30 to pray is considered fanaticism." -Ravenhill