As much as the Bible gives them leeway to do so. Not much - the Word should dictate our lifestyle.
Laymen say no, and pastors say yes.
Why would we if we can go directly and immediately into the presence of God to do so. Depends on your interpretation of entirely. They are our shepherds, thus entirely as outlined by the Word would be my response. Naturally they are all roles of the Lord, but he has delegated the running of the church to the local leaders. Not much - the Word should dictate our lifestyle.