From a purely utilitarian perspective, not really. Initially, I only did a few practise tests every now and then to gauge my skills, they thought I had a so-so chance of getting in but they also said I didn't need to begin doing intensive work that early. However, my parents still continued to send me to weekend maths and english classes, which I had been going to since prep. Coursework from the coaching college only started getting intensive in Year 8 a few months before the exam but I thought of it as no pain, no gain for a temporary time, and I also put in some independent study to get ahead of my tutor class.
I think that the coaching college was worth it because I wouldn't have gotten into MHS without it, and MHS was worth every single early morning train. The colleges are most valuable to students who would just miss out on a spot otherwise; I was smart compared to people in my piss-poor school, but going to the college made me realise my habits of making assumptions in questions, poor exam techniques etc. Many of their practise exam questions were similar to the actual exam iirc, and even with my improvements before the exam, I still only managed to nick into MHS (I had one superior only and pretty much got in because I went to a less competitive, shitty school), so if I didn't go to the college I'd probably have to languish at my old school, which I wanted to avoid and private schools were out of the question.
As for the weekend schooling I always had, they would just clog up the morning of my weekends so there was still plenty of free time. And I was never really stressed.