Yes it is possible to marinate chicken too long.
When you marinate chicken too long the chicken can become too tough and dense which can make it hard to eat or chew the chicken.
Chicken really only needs marinated for around 12 to 24 hours at most and any longer than that is not good as it can become tough and then you will ruin the chicken.
When marinating chicken you should marinate the chicken for at least 30 minutes but the longer you can marinate the chicken the better.
When you marinate chicken longer than 30 minutes the flavor will get much better and the longer you marinate the chicken the more delicious the chicken will be.
Chicken does not need to be marinated to become tender but marinating chicken before cooking it helps to enhance the flavor and make for a more delicious chicken meal.
I like to marinate my chicken for at least 12 hours which I do so overnight in the refrigerator.
But if you're marinating the chicken for 30 minutes then leaving it out at room temperature is okay.
Any longer than 30 minutes the chicken should be put in the refrigerator.
Don't leave the chicken to marinate in the refrigerator longer than 3 days though as it can go bad.
Chicken goes bad when raw in the refrigerator after 3 days and will spoil and smell bad.