All I know is maybe not to use it too much?  The previous owners didn't use it much or had it in storage most of the time. The fridge is a Traveller Elixer and I cannot find the name brand of the furnace but it looks even older or more used. Nevertheless they both work so far. The nice thing about the furnace is it is very quiet. Not loud like many report on their new units. No electricity or fan is used.  Crazily enough I found it in Minnesota which is a rust belt state that uses lots of salt on the winter roads.  Of course there is no evidence it was ever used in the winter. That would be pretty brave in a Minnesota winter.