Train hard and improve your skills, or stop training and forget your skills. Training just enough to maintain your level is the worst idea.

You reinforce your biases, which makes it harder to resume improvement later. Also, you get comfortable with being at a fixed level.

Gaining knowledge is almost always good, but one must be wary of learning skills.

Knowledge tends to come in small chunks. If a chunk turns out to be wrong, you can discard it. Skills are harder to discard, and they're always at least somewhat wrong.