To keep an attachment going over distance is to be creative in becoming as much a part of your grandchild's everyday life as possible. Then, when you get together in person, there will be no gaps in time where you did not know exactly what you both were doing. Young children grow and change quickly. Happily, this changes quickly after a couple of days together. Keeping the connection going is critically important.
Technology is a blessing to long-distance grandparents.
Lots of kids are computer literate. Grandparents must become computer literate too. Happily, the cost to buy a computer is significantly less than in the past. Faxes are useful. One grandmother we know gave all of her grandchildren fax machines so they could keep in touch on a daily basis.