Well, I am sure with DNJ on not wanting ANY harness part to break, EVER! Harness doesn’t think, so planned breaking point will sure come back to bite you. They ALWAYS break at the worst possible time.
I can not think of one wreck I have been in or watched, that breaking parts would have helped. In fact, harness holding firm, allowed people to help animal and driver out of his situation. Any loose part, give, would have encouraged horse to jump, struggle harder, getting into a worse situation.
Well broke in driving horses are MUCH more accepting of the “peculiar” wants of their handlers. Traces between the legs in training, rubbing of odd straps and carriage parts on body. Sudden lurches and jerks while pulling just happen. Noises, yelling. Not a big deal. Ours usually think this is just another weird submission thing, stand and wait quietly until someone fixes stuff.
The most important part of your harness is the hardware. Quality buckles and rings, good stitching to hold them in place. Buckles need thick tongues, so they don’t bend under pull. This is EVERY buckle on the harness. Ours are stainless steel, with stainless tongues. Brass buckles need steel tongues for strength. NEVER use brass tongues on a buckle, they bend in half very easily. Then your straps are sliding out of the buckle and keepers, horse is unfastened yet still going along. EEK!
Leather is great, yet does need regular attention or it dies. I am not sure it is greatly heavier than biothane, but weight does add up. Especially if you are over 30, have lots of years cleaning barns and riding. Shoulders get worn. It is harder to hoist heavy stuff up over a horse back. You COULD consider it your “weight bearing exercise” for improving bone density!
We have a set of 4 webbing harnesses, by Tedman. They are WONDERFUL for carting about. You can put the whole individuals harness on one arm to throw up on 17H horse. I can CARRY all 4 harnesses in ONE BAG to load for trips. Bridles in their own bag. Not the case with the dressy leather. We put two backpads with cruppers, 4 traces, the pair’s lines in one wheeled bag for show. Still heavy to pull about. 4 Collars each get their own bag. Two bridles with bits in a bag. Does make for MUCH more to pack, but SO MUCH easier manage individually. We cart each bag around because they ARE heavy. I am not making packing into an endurance contest, how much can I carry. Easy to hurt yourself with such weight and all the “up-into the trailer” trips. Then everyone has to stay home.
We also have Zilco harness, which is a bit lighter than leather. Haven’t used it much yet. Other ladies who drive like their biothane, say it is lighter. Many are older, have past injuries or problems, so weight is a consideration.
As Thomas said, you should be wiping off the harness after each use. Your hands on the straps, feeling the straps, looking at the parts, is your best method of finding problems, preventing accidents, whatever kind of straps you have. Biothane is not self-healing, or fail-safe to use.
YOU have to look at any harness stitching, check it over after each use.
I NEVER want any harness parts “breaking for safety” in any circumstances. It may be expensive, but I can repair carriages, even the antiques.
My horses wear double layer, steel hardware, nylon halters when they are haltered. Thick, heavy neckropes with expensive snaps. I don’t want that halter or rope to ever break either. Horse is well trained to tie and stand, not ever pulling back hard. I consider it much more dangerous for him/her to be running loose, hurting someone else or getting hurt, than possible dangers of being tied, hard-and-fast, where I left them.
You do your best to prevent a bad situation from EVER happening with solid basics, good horse training, good RELIABLE harness and equipment. Pay attention to your surroundings ALL THE TIME. You avoid “situations” like iffy horses and drivers at the activity you are attending.