Most imortant is that you do it because you like it. The journey is as important as the end result.
Commercial flying has large ups and downs in the past. It is likely to be similar in the future. My advice, make sure you are able to sustain yourself and keep active after you finish the training. Even if that means no flying job for months/years.
And a correction to the timelines:
18 months is the maximum time between the first and the last theoretical exam.
You have 36 months after the last theoretical exam to get the practical check for IR(or CPL).