Honestly, do as you want. If you listen to people that explain that you'll never find a job, you'll go nowhere... I'm doing my ATPL on top of my work and I'm 36. One of my friends just got 2 offers and he is my age. You will be less young that others F/Os in the job but you'll have more experience in life and certainly it will help. It is not good or bad, it is different.