When I first went to live in the UK, in 1970, initially for 6 months, which lasted almost 40 years- the world was much 'smaller'. Flights were very expensive, so travelling by train with little ones to visit my parents was a huge expedition including 5 trains, and the crossing of London and Paris with several tubes.
Those good byes with my parents were always so tough. But much much worse when they became very old and frail, and I felt I was abandoning them every time - and everytime thinking, this may well be the last time. By then of course, I could jump on the next EasyJet flight, hire a car and be with them within a few hours. I gave up my full-time job and started my own business to be able to come whenever there was an emergency. In the end, we decided to go and live near them, to be there for them. Mum died 3 weeks before we moved, and dad 2 months later.
Still, we love it here- but now we have the same problem t'other way round - with one daughter and 2 little ones in the UK, and another in Tenerife. So good byes will be with us forever. At least, again, I know I can jump on a plane and be there in hours in an emergency- and soon, the grandkids will be able to come and spend holidays with us on their own.
I would of course never ever stop them or make them guilty, but I have to say I would find the huge distance with Australia or NZ much more difficult to cope with- as I wouldn't feel that they are just a small hop away.