TTY bolts are single use only in my book, less issues if they are replaced. Only 1 has to stretch that little bit much and then you have a warped head and bigger issues. Especially in these days of OHC engines with cams running in cast bearings in the head.They are torque to yield if they have a tighten to x, loosen, tighten to x, turn another x degrees.
"Can" you reuse them? Sure. But Fel Pro says no, toss them... this is common with "late model" head bolts. Many after early 90's.
It is a BAD idea to reuse them if torque to yield.
With that being said, many folks can't properly use a torque wrench either...
(I build engines for a living.... mostly race crap.... some stock stuff if slow or bored)