it all comes down to again, WHAT the arrow, broadhead hits or NOT
when it hits softer things and has time to slow down, odds of damage is less, so many many times before NON fix able damage happens,
hit hard objects, be it large bones and or pass thru's and then rocks and such, and damages can happen in ONE Shot, that make them un safe to use
so there is NO real answer that will work all the time, each shot is different, each impact is different,!
I would';t BUY arrows/broad heads with expectations of large amounts of use , I would plan for damage with each kill, and adjust as needed
if still good to keep using, feel free to do so, but its NOT about trying to make use of things the longest, its about using what is safe to use and replacing as needed!