Urgh this does my head in. 😆 As I say, my 2 are in their late 20s and left home a decade ago, and I haven't had the 'aren't you a granny' questions yet! But I do have some women I know (my age - mid to late 50s - and some a decade older,) constantly talking about 'the grandkids,' and posting photos of them 3-6 times a week on Facebook! I have had to unfollow a few coz I'm sick of the twee 'being a granny is the best' blurb all over my feed. Some even say they prefer their grandchildren to their own children... Make of that what you will.
My friend (of 30-ish years,) who is a few years younger than me, is normally fine, and I am fond of her ... She has 3 grandchildren, (aged between 1 and 5,) from her 2 DC. They had them in their mid to late 20s.... She has said to me a couple of times, 'better tell your 2 to hurry up! Don't wanna be a knackered old granny LOL!' 😆
I know she doesn't mean anything malicious by it, but I don't want my 2 to have kids much sooner than they want to, just so that I am not a 'knackered old granny!' 
They both say they don't want kids now, but may do in 5+ years. There's a possibility they may never have them, and that is OK. My welfare, and happiness is not dependent on having grandchildren!
Also my friend who is only just gone past 50 spends a lot of time looking after her 3 grandchildren! Both of her DC use her as a free babysitter. She is tied down every week with babysitting/childminding, (as well as having to work 22-23 hours a week.) She fits this in at weekends and evenings so she can babysit her 3 grandchildren. LOL, fuck that!