Good questions. First off, this is a 50th birthday present from my wife (cool life event). However, I take 5 - 8 lessons a year from my local PGA pro (last five or six years). I agree with how long it takes to incorporate or understand something you learn in one lesson. I also agree that a week long series of intensive golf lesson will throw more info than I can handle.
I'm a 10.9 index and have been as low as 9.0. I'm excited more about the prospects of short game and on-course instruction. My local course has limited practice facilities (like sand traps, large putting greens) and doesn't offer playing lessons. I'm also hoping they offer strategy and approaches towards my game than just swing mechanics. It will be interesting to have a fresh set of eyes evaluate my game. Lastly, it will be nice taking lessons while on vacation versus rushing to a lesson hyped up from the work day. I'm not expecting miracles but I hope it will be a good experience. It's the Pinehurst golf school.
Thanks again for your questions.