I've been using this same Yakima Trailer going on 2 years, and the person I got it off of had it for around 2 years. I would say it has well over 100,000 miles on it because I've put around 30,000 miles on it in the 2 years I had it, and the person I got it off of pulled it a lot more than I could ever imagine.
It has the heavy duty shocks, and on the 2,800 mile trip we had 4 kayaks loaded on it that weighed around 320lbs with paddles, rods, tackle trays, PFD's, stakeout poles and any other gear we could fit in the kayaks, so I would say we had close to 400lbs on the trailer.
In one week the year before last we put over 2,800 miles on it. Last year it took several trips to south Florida From Tennessee, and a couple trips to South Carolina, along with countless trips to Georgia, Alabama, and East Tennessee.
Before we start up this season I'll be replacing the wheel bearings, and axle bolts and going over the trailer with a fine tooth comb to ensure everything is safe for travel.
From the research I've done it looks like the best thing will be PVC runners, but not sure if I want to go 4" or 6" and 8', or 10'. I'm definitely going to check out the Hobie cradles also, but I cannot get them spaced to the recommended distance.