When to change hoses on a Diesel Pusher ??

Rubber products don't really care about mileage. Even parts sitting on a shelf long enough will start to harden. It has to do with the environment and how much ozone they were exposed to. Usually a simple inspection should show if the rubber is still pliable and not cracked. Also remember that more and more hoses are being made of silicone and will last a lot longer than the older rubber hoses.

Which hoses? Hydraulic? Radiator? Brakes? Fresh water hoses?

Generally I like to say "when they go bad". For reliability from A to B it is better to check radiator hoses. They should be springy not squishy/mushy.

We had the hydraulic hose burst after about 17 years. No fun to lose the power steering and the cooling fans. Get any hydraulic hoses changed ASAP.

Had major work done on my '94 Cummins and asked the shop about changing all the hoses...they kind of smirked at me. Had 128,000 miles on it. They did humor me and pulled off a rad hose, inspected it, and said it was good for another 100K.

Had the tranni hose pulled off when I had the standard tranni fluid replaced with Transynd and they also said the cooler hoses were fine. Also was over 100K at the time.

Yours does have the higher pressure hydraulic system so maybe have them looked at when you get to 100K?

JMO

Well, my Dutch Star is a 2002 which I bought in 2009. I have no way of knowing if the hoses were ever changed out. However, when I had the rig out at Spartan chassis in Michigan last summer to have some work done, I also had them do their 100/point inspection as well as do a coolant flush and change. They said the hoses looked fine and in good shape. None the less, I bought a set of spare hoses from Spartan and keep them on board, just-in-case.