So I have entered my 10th year of teaching (how I am not sure, actually I cannot believe 10 years has already pasted, but that is another topic for another day), and most educational "people" would say that those years make me better. And that I agree with - so as I prepped for the first week of school - prepared my room, my google classroom (my virtual room), and many details with the telepresence course I teach - I decided to use my daily plans from last year for the first 3 days. I am always thinking about ways to skip good to do great - reusing did NOT result in great.....
So this experiment I ran with planning just did not work. I felt under-prepared, it took me 10 minutes to plan 3 days by "re-using" (copying) last year's plans. I typically would take 90 minutes and I now know with certainty that I must give that time and thought to each week. It is a combination of planning and reflection, where reflection of how to teach and reach the students is my driving consideration.
So the plan was there, but the reflection was not. It kept me from having the insights, often when planning I think about misconceptions, vocab, common errors - when I just reused the opening days I missed those thoughts and thus felt like I was chasing my tail during the lessons (FYI - I teach the very first day -- I do "class" stuff, like rules, etc later -- we have math to do!).
So even though I have more experience, shortening planning time is not a trade of good for great. Planning time is a requirement of great.