I generally look at the data on the specific product. If it's been discontinued for a year already and new model has been out for a year and it's still selling, that tells me something.

I look at a lot of things, and like I said I don't just do discontinued items.

Right now I'm holding onto some Samsung Blu-ray players from 2015. Samsung stopped making them, so the 2017 models are the latest, but the 2015 are cheaper and still selling quite well. I expect the price to go up a bit as the other guys selling it sell out, and then I'll make maybe 30-40% on my money for holding it for 4 months or so, minus costs/returns.

Very doable if you have capital and are willing to be active and take some risks.