Sometimes I think the Holy Spirit gets blamed for a lot of human inadequacies.
When I first started out, I wrote my Sunday mornng sermon on Saturday, and finished my evening sermon Sunday afternnoon. I studied all week. I also always had a three or four point alliterated outline with subpoints as well. These were my pulpit notes. I also wrote sermons out in full for filing.
During the week there were funerals and weddings, I lectured three times each week, Wednesday night Bible study, and other weekly meetings, plus invites to other churches. I don't know how many hours I had in preparation of each sermon, but I only slept about 3-4 hours each night, and often worked through the night and caught a kip in the afternoon.
Some might say I preached topical sermons, but always kept my selected topics within the context of the text at hand......So, is that really topical? I never paid much mind to what format my sermons might be labelled.
Because I swallowed the Oxford dictionary, I was very careful to find the simplest words to express my thoughts in public. If a child could understand me, so could the lawyer and doctor.
The key is that we prayer beforehand about what we should preach. This, in my opinion, is when the Spirit of God leads, and not to substitute for our inadequacies in preparation. If He gives me the sermon beforehand, I shouldn't think He would change His mind whilst in the pulpit. That is my opinion on the matter and would not dictate to others. Each person is unique, and not monkeys aping others.
Cheers, and preach the Word,
Jim