Summertime in the MidWest can dull the sound of MLs a bit...but over the long haul...smoke and/or cooking fumes can do some real harm.
If you ever look at buying these guys used...they need to be from a smoke free home..and hopefully were far enough away from the kitchen to not have had to deal with the oils and smoke that get into the air....if you can smell it..there are gases in the air that will become solids when they cool and come in contact with walls....furniture..and the panels on MLs.