When you look over at your customers neighbor's condenser after you just fixed his on a 95 degree day....and see that the suction line has an inch of ice around it....and a smile comes across your face.....
You're sitting in a movie theater waiting for the movie to start...and you can't help but hear the RTU compressors humming overhead.
You can tell a recip and a scroll apart just by sound alone.
There's a thermometer stuck in one of the dash a/c outlets of your truck...permanently.
You walk into a friend, relative or neighbor's house and your eyes immediately start scanning for the supply and return registers, what type they are, and grimace if they're placed wrong and/or are the wrong type.
You're inside a huge, cool, domed stadium on a hot day, and you can't stop wondering how all that space is air-conditioned.
You see your wife/girlfriend freezing in a cold draft when you're both sitting at a table or booth in a restaurant, and your eyes immediately find the source of the offending breeze (offending to her, anyway. You're probably happy as a lark )