Agree with Ed T on about all you can do to delay the inevitable. Equipment in salt, fish/meat packing, fertilizer etc will not hold up well - corrosion just eats up the machines period up. Keep the oil & grease on them.

You mentioned you have rentals in this operation -I hope you are getting your standard rental rates plus a lot more.

My experience is with meat packing and found that these companies like to try one of every make in search of one that will hold up well and buy it at a reasonable price. I don't happen. Within 6 month a new machine with stainless steel or nickle plated harware shafts wear out just as fast as with the factory standard stuff and the truck looks to be 8 or 9 years old or more