I had Towmax on my Sundance until earlier this month. Same size as yours. I just replace them with Maxxis.
Since I purchased the rig second hand, I don't know how many miles were on the tires. But, because of all the bad press, the first thing I did was weigh my rig. It came in at 6600 lbs. (axle weight only.) Since the tries are rated at 2450 lbs @ 65 psi, I felt I had enough margin to take the risk. But, I purchased a Tire Pressure Monitoring System and was religious about checking the tire pressure. I put about 10,000 miles on them myself. But form what I have read, when tires reach 5 years old, they are more susceptible failure due to internal rot, no matter how good they look on the outside. So, it was time.
If you do nothing else, I would recommend you invest in a TPMS.
Also, if you want to delve into more than you ever wanted to know about tires, you should visit Roger Marble's blog on RV tire safety
here