Having been the grandchild in a similar situation, albeit in a place and an era where we relied on letters rather than the phone (I am 53), I would support what a lot of people have said about how you can maintain excellent relationships with grandparents. As a family, we stayed with Mum's parents on long leaves, and my grandparents were our guardians when we came back to boarding school in the UK.
I recently had the chance to read my grandfather's dairy for the year in which I started university in the UK - parents still abroad at that time. I was amazed at just how often I and my sisters visited, from school and university. It didn't stop Grandad complaining about our flagrant use of his electric heaters though. We were raised in the tropics, and he turned the heating off if it was above freezing!
Looking back, it must have required a fair amount of mutual tolerance - when we stayed as a family, it was for several months. And I have to admit the relationship was better with my mother's parents than with my father's. But I think that reflected long standing tensions between Dad and his parents, more than the long distance lifestyle.
Now, I live in the UK but my two sisters live in the USA and Australia. My Mum had to cope with much loved grandchildren moving to Australia at a time when my father's health was failing and she found it very hard. But my sister and her husband have had opportunities there which would never have come their way in the UK. My neice gets married there later this year, and we are all hoping to make it to the wedding.
Mum moved last summer to live close to me and my family. It is the first time we have been able to see each other every week since I went to boarding school aged 11. It is taking some adjusting to, but we are all enjoying having her so close. She recently went to visit her brother in Canada, where he emigrated in the early 60s.
I guess there must be a very dominant 'itchy feet' gene in my family, but we do seem to manage to maintain the relationships long distance over very long periods of time!