How do you keep an online friendship strong?

My best friend Ahsan lives in Saudi Arabia. We have known each other for two years, and we talk every day. He listens to me, and he understands me, and never once makes judgements. We talk on skype and we are there for each other. He has helped me get through so much. Lately though, I feel like I've been bothering him a little, you know what I mean? All the same, he's wonderful. He knows my deepest secrets, and he keeps them safe. I call him sometimes, and he makes me laugh, when I don't even feel like smiIing. I was wondering how to keep our friendship as strong as it is. Maybe some new ideas of things to do? Thanks very much, in advance. :)