I became an expert in a very niche technology and the only thing I did is do the same for 6 years. For the first project, there was just no one else to do it, s

I became an expert in a very niche technology and the only thing I did is do the same for 6 years. For the first project, there was just no one else to do it, so my company hired an extremely expensive contractor and I collaborated with him. After that I supported the product and implemented solutions with the same tool for other lines of business in my company. After 4 years of doing it, I became probably one of the 10 or even less best experts in the world with this product but I was really tired of it. The technology was already outdated but still alive, so before giving up for more interesting things I became freelance during 2 years and got paid 4 times my previous salary. It was painful and boring to keep doing the same but it helped me to pay my house. I could have extended it for 2 or 3 more years before the technology died for good, but I was so tired of it that I decided the money was not worth it anymore and I started again to be an apprentice of the technologies I missed during the 6 years period of being an expert in a very single thing. Now I still struggling every day because I've been learning too many things but I still didn't have the chance of a long term project that helps me become an expert.