[ke0me]

Since I haven't used Duro before, I would only echo what others have said:

1- be paranoid about proper inflation at the start of every trip.
2- slow down, trailer tires do not dissipate heat as well as regular truck and car tires, so heat is a real killer.
3- I always balance/rebalance the trailer tires, it just doesn't make sense not to.
4- Your supplier is very good to spec tires that a good amount under maximum rating.

If your spare tire is 8 years old also, I would buy 5 tires, not 4.
Enjoy the new tires.