Eh, not necessarily. Like I said before, the cables are really the only things you need to worry about in that area. When you consider how each of the components works, it makes it seem less damaging.

The heat cartridge is just two cables touching together inside a porcelain and metal housing that gets hot.

The thermistor is just two cables slightly air gapped inside another porcelain and metal housing to provide varying resistance depending on temperature.

Neither of these components will care if a huge blob of plastic temporarily adheres itself to the housing, so long as the cables remain intact.