For me the first time was the best, I managed to quickly come up with an idea and grind at it. Never learned so much before in a short time. I tried 1-2 jams afterwards but the ideas I had were too hard, at least at the time, to execute on, and never really had the time to push forward properly. However, every single time I tried to make something for a jam was an effective learning experience.
If I look at the code I made for the first jam now, I’m amazed that the game even held together with all the spaghetti. I guess not knowing better is a good thing sometimes.