I give birthday and Christmas presents to all my children, grandchildren and great children regardless of age. I can’t imagine not giving them a present just because they grow up. Unless a gift is given face to face, it’s rare for me to get a thank you from the older grandchildren but rare not to get a thank you from the younger ones who I imagine do it at their parent’s behest. I don’t begrudge the lack of a thank you (but I do notice it) not am I ever tempted to stop giving gifts because I don’t get a thank you in return. Family is family and I try to treat them as I would like to be treated.
Friends, acquaintances, nieces, nephews etc. are another matter. The latter get presents until they are 18 with no thank you strings attached. The former only get presents if I wish to buy them something and a lack of a thank you would most probably mean that I didn’t get the urge to buy anything the following year.
I always buy something for family new babies and thank yous sometimes come and sometimes don’t. I gave a niece what I thought was a generous monetary wedding present recently but got no acknowledgement at all. I thought that was very bad manners since I think wedding presents should always be acknowledged.
I think the best attitude to take for ones state of mind is to give without expecting anything in return and, if you can’t do that, don’t give.
I hope that doesn’t sound too trite.
I know from experience with my own children and my mother who didn’t really bother with them at all ever, that the child and grandparent relationship can sometimes be a strained and rather remote one. I think a lack of contact especially in the early years prevents the strong bond which we would all like to have with our family members.