I have 2 DGC, both the children of my DS. They live 200 miles away and we see them about every six weeks, usually for several days at a time. As not just DGC but their parents are in education, as pupils or, in DS case, university lecturer, we generally visit them in term time and they visit us in the holidays/vacations.
They come to us for up to a week at Christmas (although only every other Christmas day), Easter (ditto) and summer holidays and we go up for birthdays, special events, occasional child care and when our own lives take us north of Watford.
DGD has been coming to stay with us once or twice a year since she was 7 (she is now 9) and will be coming next week for 5 days and she has been on the phone several times to tell me how excited she is about it and discuss the things we will do together. We will collect her but the rest of the family will come down at the end of her visit and will stay with us for a week.
DGS, aged 6, has not yet visited on his own, or with his sister, as he has had health problems, now gone, but his parents are understandably still a bit nervous at his being too far from home without them.