It depends if it's online or irl. Online friendships are highly variable. You could talk to that person once a week, once a month or every few months and still maintain the friendship and be able to pick up where you left off with that person. You don't spend physical time together so there isn't that feeling of "oh geez, I haven't seen you in so long, we need to catch up" after a time apart. I love this flexibility of online relationships. It is especially nice for those of us that have minimal social needs. Online friendships are easy to start. There is no courting process like there is in real life. It's like "hey wanna chat? Okay!"
A real life friendship has higher expectations in my opinion. What many people call friends I might be more likely to call aquaintances. The majority of my friendships have been honest and intense. To me a friend is something of a platonic soul mate. Someone whom you feel a deep connection with or someone who had a profound impact on your life. Often friendships take a while to blossom but I have a habit of having short, intense friendships before we go our different ways (though, almost never because of a falling out). To me a friend is someone you never forget.
This is a great topic btw. Looking forward to hearing the responses.