Hi Teach,
You have been good about the tire pressure, keeping them covered and stored up on boards, those are all excellent things to do.
And I know you have been around mechanical things a good long time. But we are talking about ST trailer tires here, not a older well kept auto.
There are some things you did not mention that may help you make this decision like,
How many miles are on the tires? Not a direct part of the answer, but we all camp differently and do not know how far away your trips are.
How long are you common camping trips? 5 miles, 50, 150 miles? When you get towards the 50 mile mark, the tires heat up and then things can happen if the tire is starting to degrade inside.
Have you weighed the camper and know the "loaded" ready to camp weight of the heaviest wheel?
Do you know the weights of the front axle loaded with the WD hitch engaged? The WD hitch adds extra weight to the front axle above the weight of the camper.
Do you have 20% extra rated tire capacity above the weight of the heaviest wheel location ever since the tires were new? This helps deter interply shear inside the tire trying to tear it apart when turning on tandem axles.
Assuming some of the above items may not be known right now, have you done a spin test of each tire? This is a prudent test to do as the tires age, ideally every year since new but for sure come year 3 and on. See this reply on the tire failures I had last spring. It talks about the interply shear and how to do the spin test.
Tire Failure, Tire Investigation and Camper Damage Repair
If I had done a spin test before I headed out in the spring of last year, I could of avoided my saga. I can guarantee you, I will never miss another one. Unless you have a lot of excess capacity in the tire since they are new, at the 20% and above the rating, the interply shear forces are there and acting on the tire on every turn. This does not matter if the tire has no cracks in the treads or side walls. They only aggravate the problem worse. The rubber is breaking down inside the tire.
Bottom line: Come this March your tires will be 6 years old. That is a year past the 5 year mark. As a fellow camper, to put this simply, it's great you made it 6 years, but consider it good fortune you made it that long. It's time to change them before you head out this spring.
Hope this helps
John