I was fortunate that I didn't get the usual facial hair pattern of men in my family, with very heavy full beard. Mine was mostly limited to the goatee, moustache, and sideburn areas. That said, I've done about 60 hours / 50,000 hairs so far, and I'm guessing maybe 10,000 to go. Some people can have as many as 300,000 hairs if they have extremely heavy and full beard growth, so faces will vary greatly.
By the way, I take a couple of benadryl (diphenhydramine) over the counter allergy capsules half an hour before each session. It goes a long way to reducing redness and irritation from the treatment.
I'm no expert, but I believe the plucking occurs most often when not enough energy is being delivered to the base of the hair. Many practitioners use the smallest needle and least energy they can to reduce irritation and discomfort, but tradeoff may be more re-dos. My practitioner (Jaimee Bloom) makes no apology for using larger probes and more intense settings as needed to get them the first time, though you can look like you were attacked by bees after a long session. 😉 To me it is worth it.