[mauvehaus]

What will put them out of service in fairly short order is salt exposure from carrying salt.

Cargill has a big salt mine in Cleveland that extends several miles under Lake Erie[0]. I don't know where else they're mining it, but it gets shipped in lakers, and it's pretty rough on them for obvious reasons.

I toured the Mather[1] some years back (take the below decks and engineering tour if they're offering it), and the guide made a point that the fact that the Mather hadn't carried salt was a big factor in how well-preserved she is. Carrying salt is apparently the last stop before the ship breakers for a lot of lake steamers.

[0] http://www.rockthelake.com/buzz/2017/12/cargill-salt-mine-cl...

[1] https://greatscience.com/explore/exhibits/william-g-mather-s...

[rpeden]

The world's largest salt mine is underneath Lake Huron near Goderich, Ontario. I believe lakers pick up loads of salt there as well.

[zoklet-enjoyer]

Fun fact: I went to school with the CEO of Cargill's kid. Huge douchebag

Edit: Just looked it up and he hasn't been CEO since 2013