The grandparents are fun to be around, and as far as how long skinwalkers can live, we already know that Isaac is well over 100-years-old and rapidly approaching 200, and eventually we'll be told how long skinwalkers can actually live. Just be patient.
Yes, living a long time can have its advantages, but it has its disadvantages as well, such as outliving some loved ones and many friends, and I'm sure it is very difficult to find a spouse that is willing to accept your strange ability and the fact that you don't seem to age, although you can make yourself appear to age.
As far as the names, Isaac chose Jacob's name and may have been influences by the Bible, as well as Jacob calling his son Aaron. However, Aaron changed all of that when he named his son Devin. I'm glad you enjoyed this chapter.