Stop in for a cup of coffee

Had Stihl in and out of shop, they replaced carb said it was all corroded, not sure why they missed this first time. I always use ethanol free gas but they said moisture can be absorbed by gas in the can. My two-cycle gas can does have an open spout and maybe it sits a bit at times before use. Anyone heard of this, I've never regularly used "gas dry". Maybe I'll change my gas can to a sealed, dunno.