Pertaining to drysuit diagonal front zippers used with weight belts, here's a little more info that might allow some conclusions to be drawn....or it might just raise more questions....
Background: I've only used DUI diagonal front zip suits (TLS350 and CLx450). Zipper care was consistently good for both. They were used almost exclusively for shore diving and were subjected to the typical stresses of walking fully geared up, including a weight belt.
On the TLS350, I needed to replace the zipper after using it on 230 dives.
On the CLx450, I replaced the zipper after using it on 434 dives, although it first started leaking after around 350 dives.
In both cases, the source of the small leak was in the area that had the greatest visible wear, that is, an inch or so above the zipper dock at the lower right hip area. From talking with others, that's typically the area of greatest wear for diagonal front zippers.
That area coincides with where the zipper crosses the waist, creating the most severe bending point for the zipper, as suggested by the OP. It also coincides with where the weight belt crosses the zipper.
Regarding my weight belt, I usually had 34 to 38 lbs on the belt, so the stress was considerable, especially when walking.
To reduce that stress, with the CLx450 I always used a home-made weight-belt harness, so the weight belt hung from the shoulders and did not squeeze or pull on the zipper much at all. The wear was significantly less as a result, but was still worst in that area where the bending of the zipper is most severe.
My conclusion is that zipper wear will vary depending on the stresses of bending, pulling, etc.
The location of the zipper should matter then, right?
Consider that both of these suits are the older DUI design with the zipper crossing the waist and ending up near the right hip. Beginning around 2002, I believe, DUI zippers no longer went below the waist, but instead stayed higher in the flank area. Plus, instead of the closing dock being at the lower end, they placed it at the shoulder area, but I'm not sure that affects zipper wear.
Has anyone found that DUI's newer design provides better zipper wear? Is that why they made the design change?
Also, regardless of suit cost, aren't most drysuit zippers from the same manufacturer or at least of the same quality and tooth size and design (8TZ)? If so, wouldn't it stand to reason that shoulder zips would wear better than diagonal front zips?
Has anyone found that to be true, that shoulder zips last longer?
I don't want to take over the thread, but how many dives have people gotten out of their diagonal front zips?
I'm so cheap, even 300 dives seems too short.....
Dave C