Just pull the mouth pieces, so they don't warp. The filler and carto body have no problem with hot water. I don't bother keeping the heat on, though if you did, keep it at less than boiling. I leave some space in whatever I'm cleaning them in, so I can top it off with cold water before pulling them out, to not get burned. After removing, blow through them -- if the resulting cartos look/smell OK, you're set to dry them, else repeat the boil/soak. End of the day, I probably have about 80% good for reuse after one cleaning cycle. At least 808 cartos are pretty cheap, so I don't sweat pitching them out if they don't come out good; I also just put a little juice in a cleaned carto on first use, to make sure they're indeed OK -- it bites to do a full fill only to find out the carto is dead/bad.