This is so true. I thought I could finish my first build in a few weeks as I am essentially retired and can work all day. I only got a the gloves, boots, and forearms done in that time and I worked non stop with little sleep and breaks. That was a year ago and I just finished (mostly) my suit. It didnt take a full year to finish it but I had some burn out and had to take a break. So I would say probably plan 3+ months minimum if you work in your spare time and want to get the details right/make it look good. The break and taking my time allowed me to learn new skills and buy new tools, so it was good. And I still had to remake the chest peice because of sizing issues and I'm not happy with a few peices (I feel like the shoulders are slightly too small, the thighs too big, and the boots just too roughly made since I made them first) so I will likely remake them too.
So take your time. Take a break if you need. Learn, practice, watch YouTube videos and buy some tools. But stick with it and it's totally worth it! But amazing work so far, keep it up!
