Going Back to School, but Now Working Full Time

I will be going back to college again because the program I will be in is very relevant to my job. Currently waiting to see whether my boss can pay partial or entire tuition. However, I hate going back to school again and this time it will take longer (4 years as opposed to average 2 years in program) since I work full time and have my family to take care of. To drag school longer than the actual program makes me feel incompetent as I am so used to finishing school on time or earlier than my peers. Perhaps I am just worried I will become less motivated procrastinate for being back in school too long, but then again would rather have a life around my family than being preoccupied with studying...