Does FUE permanently remove grafts for future procedures?

I have had FUE procedure 2 months ago and was thinking of having another for my beard. Was curious how long I’d have to wait before another one, and whether the back of my hair could be used again for my beard. I came across some articles that really concerned me, mainly about most people have a limited amount of grafts they could use in their lifetimes, usually around ~4-6k

Some remarks that I’ve read from doctors on this topic:

You can have many FUE procedures over your life time as long as you keep your total donor hair supply in mind. If your donor hair supply is 6000 grafts You can have six 1000 graft surgeries or three 2000 graft surgeries.

I really don’t understand the science of this works. The hair on my donor area is completely full now after 2 months. Is this in spite of some hair follicles permanently removed, and the full hair is due to remaining follicles after 2k grafts taken from there? I was under the impression that what was taken from the back would grow back. Is this not true?

FUE removes grafts from your permanent zone forever. You have a limit of donor graft supply and a good doctor will measure that limit and should quantify what your total available, lifetime graft supply will be.  For many people, large FUE sessions will cause a balding, see-through donor area as shown here: https://baldingblog.com/collection-victim-photos-internet-harvested-depleted-donor-areas/ As you can see, either these men had incompetent operators, or greedy ones who left some of them balding forever in the back of the head. For the advanced balding patterns, strip surgery (called FUT) is a better option as well as for most women expect for those who have very small procedures.