Let me join in as a pastor.
1st- Never judge a man. You do not know what battles he is fighting because as a pastor, He is battling not just his own but everyone else's as well.
2nd- He can take whatever time He needs to be filled, How can anyone place a time limit on God? He may in fact be chasing rabbits, or he may in fact be onto a spiritual breakthrough that will cause a great awakening in the church.
3rd - Do you pray regularly for your pastor? He is a warrior and is under the spiritual gun daily by many unseen spiritual battles and they take their toil on us. [Believe me]
I study every day and yet there have been many times when I got up to preach that I preached something entirely different than I even studied on, because the Holy Spirit steered me to something that was needed.
I hope this pastor is using this time to pray and be in the essence of God which is to me is even more important than studying, because when a man is bathed in the Spirit, He will speak God's Word clear and in truth and order. [No I am not talking about tongues lol]
You might ask his armor bearer to go with you and speak to him privately and offer to pray over him.
Please pray really hard for this man.
I am sure he would appreciate the fact that you care enough to ask him how he is doing :]