I wouldn’t do it while installed on the printer, but I routinely heat up my nozzles with a lighter or a heatgun to clean them up/unclog. I had a stubborn mix of PLA/PETG that would not surrender to anything less than a long application of a butane torch.
As for your longevity question - I’ve gone through a nozzle every 2 months or so on my printers, but I do a lot of printing and a lot of ironing. They are certainly considered a consumable part, and I make sure I have at least one spare at all times. Back in my Ender 3 days I would replace them often because they were like $.10 a pop. I would definitely recommend hardened nozzles if you are wearing them out quickly.