Hello all (first post),
I think it all depends on what shape your swing is in when you start the lessons. If you're hitting the ball decently but want lessons to get more accuracy or power, you may just get better if it's a small adjustment.
If your swing has a flaw(s) that requires a timing adjustment to compensate, I would think you'd get worse (maybe a lot) if you tried changing that.
With my youngest kid turning 18, I am just getting back into golf after nearly 7 years away (went golfing about 5 times in that span). I've been working hard on my swing and short game (range/practice green nearly everyday for at least 1 hour), trying to only encorporate changes that are sound. I've found a couple things and now am hitting the ball decently while shooting around 90 with a couple rounds in the low 80s. I was tempted to keep fiddling with my swing to make it a text book swing but I think I'm going to 'love the one I'm with' for right now and then come winter, revamp it. I want to enjoy my play time right now and just try to work on scoring.