Re: example of bean count failure
"Enter the bean counters who each year rite off a part of the cost of this part until after 4 years it has no value and is thrown away and removed from stock."
Bean counters should value it as a true and fair value - which would be something like the lowest between resale and scrap values. Write downs each year are more to do with offsetting against tax.
Throwing something of actual value away because an arbitrary paper value hits/nears zero sounds more like a problem of employing idiots than anything to do with bean counters.