Hi there!
My perspective is a little different in that I'm the one who moved away from my grandchildren, moving from Scotland to Sweden a little under 3 years ago. My eldest grandchild (my daughter's first son) was 7 at that time and I had him every other weekend up until I moved. My daughter lives in Denmark and her son currently still lives with his father, whom she split up with when her son was 4. I made the decision that I had to be the one to keep the contact as much as humanly possible because it would be all too easy to lose that, not being biologically related to the custodial parent. My son and his wife have a 2 year old daughter and they're still in Scotland so it cut me to the core not to be able to be close by to share in her earliest days, but that was the price of my decision to move away. As others have said, Skype is brilliant and I travel over to see them all as often as I am able, even if it means little more than a long weekend. I also have my grandson over to stay every school holiday and I'm ecstatic to report that he'll finally be moving across to join his mum this summer, just in time for the birth of his little brother. I'm now looking forward to having both my grandsons, little and large, just a short train ride away over the Öresund bridge. Being a long distance grandparent is hard, hard, hard - but the compensation is that time spent with the children is eagerly anticipated by all parties and precious beyond words.
Alex will be moving across at the end of June and his little brother is due in July. August will see a big family get-together in Denmark, the first time I'll be able to cuddle all 3 of my grandchildren together. I can hardly wait!
Now, if only I could persuade my son and his lovely wife to move over here, I could have all 3 of my precious little bunnies close at hand.... bliss