Furnace Tune Ups

[Stephen E.]

I now have a number of units with gas fired furnaces. (My others are electrically heated, which was quite common here until recently.) I have been wondering whether I should spring for furnace tune ups once in a while, say every 2-3 years for each unit. Since this is a potentially recurring expense of several hundred dollars I thought I should check with the BP community. Do you pay for furnace tune ups for your units? Do you think this saves money in the long run? Or do you just leave things and call maintenance when needed? All comments welcome.