I got into the same racket around the height of the China supercycle M&A binge and it was awesome (buyside), but even back then everyone warned me it's the kind of sector that booms once every 20-30 years. I started lobbying hard to diversify into adjacent cyclicals and eventually took on industrials all the way from bldg mats to automation; that came in very handy in periods when no one wanted to hear anything about metals. Another angle for me was to build across-the-board expertise in commodity quant from gold to corn to oil, which always kept me generating macro research unrelated to metals. So from covering metals, I ended up getting brought in to work on EM mandates as the commodity side forces you to maintain regional forecasts for China, India, Brazil etc. and keep track of all the macro news, so you're always in the mix, particularly when things flare up. That said, on the sellside you run a higher risk of getting pigeonholed; but I do admire sell-siders who were able to reinvent themselves profitably by being early on a new sector (cannabis for example) or simply lobby to take on new coverage outside their sector to hedge their careers - it's not uncommon.