I hate to break it to you, but here are some ballpark figures based on what I've seen in almost ten years of gaming on IRC/OpenRPG:
- At least half of all online campaigns fold within 4 months.
- At least nine out of ten online campaigns fold within a year.
Why do online games come and go so quickly compared to tabletop games? Well, because in a tabletop game, the players are usually real-life friends with mutually shared interests and activities outside of the game. There's a very real social bond connecting the participants.
Online games lack that bond, and generally fare better when they are started with the knowledge that there's going to be a clearly defined end to the game. Preferably, that end should come within six to eight months. And six to eight is stretching it, in most cases.
The ancient simplicity into which honour so largely entered was laughed down and disappeared; and society became divided into camps in which no man trusted his fellow. To put an end to this, there was neither promise to be depended upon, nor oath that could command respect; but all parties dwelling rather in their calculation upon the hopelessness of a permanent state of things, were more intent upon self-defence than capable of confidence. In this contest the blunter wits were most successful.
- Thucydides 3.83