so what do you want them to do, more then they have been doing?
even if you said every ride needs to be demolished, replaced, and rebuilt after one year, that will not completely eliminate the possibility of a failure/accident, nothing will, its impossible to do that,
a time frame can not be established, quality control on manufactured parts can only do so much, you can not determine a part will last



number of days before it has fatigue cracks, you are asking the impossible,
you could build two rides exactly the same and place them side by side, one might have an accident after 30 days, the other might last 50 years, you cant determine that, or predict that,
its the same if you go into a store and buy two of the exact same TVs, one might crap out after 6 months, the other might last 20 years,
buy 2 of the same car from the exact same dealership, one could have all sort of problems after 6 months, one may never have problems,
you cant inspect every ride with a magnifying glass every day, even that will not make a difference, stress cracks could appear throughout the day,
the only solution is to have the ride inspected with a fine tooth comb after every single ride throughout the day, which would take hours, and thats just absurd
we dont live in a perfect world and we never will