My friend lives in the Sunshine Coast in QLD and his daughter lives in Melbourne. His daughter is 7 and they are very close. He flys down to see her every two months or so and they Skype every second day for him to help her with homework and to chat. He also bought her a mobile so she can call or text him whenever she wants to.
My ex moved away and rarely contacts my daughter and his visits are sporadic. She doesn't really have much of a relationship with him, although she is only 3.
My advice would be to be constant and consistent with contact of your girls. Make sure they know you love them and that they are still important to you.