I have a Kenmore furnace that was installed in May 1999, cracked heat exchanger March, 2010. Sears did the repair and it cracked again in De. 2010, repaired again by Sears. November 2012, had a Trane installed, there were big holes in the exchanger?
Would it be common for 4 heat exchangers to go bad in 13 years?

Thank you in advance,

Something is wrong with the install of those furnaces. You might have a restricted return among other things. Get a good contractor and have them look over your duct work because losing all those heat exchangers is not normal.

Something is wrong with the install of those furnaces. You might have a restricted return among other things. Get a good contractor and have them look over your duct work because loosing all those heat exchangers is not normal.

Agreed 100%. If no other changes were made & the Trane is the same capacity, it too will crack.

Do you ever set the temperature way low when you are gone for a lengthy time like on vacation or long weekends?