I live for my two visits a year. In between I talk on the phone every week with the 2 older ones. I don't always understand what I am hearing, but just hearing their voices helps. It contains pictures of me all over town and is decorated with Disney pictures from an old wall paper book.
Most wallpaper stores are more than happy to give away old books.
One granddaughter brings the book to the phone and shows me the pictures. It is hard to leave, but it would be even harder never to see them. While they can't understand yet why grandma doesn't visit all the time, the photos help them to remember who I am until I visit again. We have two granddaughters and each has their special name for us. Kelly, the youngest calls me Mema and my husband is Pop pop.